The most important thing for the first season is to establish a healthy root system. Vigorous vines can also establish a healthy trunk (at least pencil thick all the way to the fruiting wire) in the first season. If not pencil thick, cut it back to 3 buds and start over.

The growing season after your trunk is established you should concentrate on the cordon arms (also pencil thick at the ends). Allowing a vine to fruit at this stage may compromise your growth and result in weak cordons. Some vines can support a cluster or two, but it is generally recommended to remove the fruit until the cordons are established.

These are long lived plants, so getting the core structure right is pretty important. They will be easier to maintain and result in better performance in the long run.

How are you training it? There are many different ways.
Backyardener's advice is for cordon training.
If it was me growing table grapes I would be cane training 4 arm Kniffen and would've stopped it growing up before 8' to start working on canes for next year's fruit.

I've got first year rooted grapes from the nursery that I expect to produce a full crop next year. They grew up the 6' to the top of the trellis and the 4 canes have reached their limits in filled in their half of the trellis.

What you at least should've done if you are cane training is to leave 4 spurs at the points you want the canes to grow.
You should probably not allow it to fruit next year if it tries, no matter how you are pruning it since you don't have canes or cordons trained.

This seems to be a strange time of year to be asking this question. Pruning is in late winter, flowering is in spring and fruit harvest is about now.

Growing against a fence may be a problem. Chain link is hard to clean them off. Solid privacy fence cuts airflow and encourages disease.

I'm curious why you would recommend cane pruning for table grapes. I know some varieties require it because they don't produce fruit from the first few buds, but I don't think Niagara is one of them. All of the commercial table grape growers that I know (here in Idaho) spur prune their vines, unless they are growing one of those few varieties that require cane pruning.

I didn't recommend cane pruning for table grapes, I said that's what I would do. I smoke but don't recommend anyone do that.
I asked what Trishmick's desired training method was so that the answers could be catered to those desires. I would rather give answers that suit desires than push my desires on others (otherwise you'd all be espaliering your apple trees :) ). I don't care if Trishmick wants to have a cordon along the top of a privacy fence or 4 canes along a split rail. I care that she gets the correct information.

I would cane prune because that's how it's generally done for homeowners. It's what I was taught in highschool horticulture, it's what my parent's had, it's what I see anywhere I see backyard grapes around here other than the occasional arbor. I've never seen a problem with it and it's easy to do. It's first in line for homeowner training methods I've seen from anywhere for table grapes.
I think it's the first recommended method because it is easy to get right for the pruning amounts and fruiting amounts to get good fruit and reliable yearly fruiting.
Assuming you're a homeowner and not a pro my question would be why do you prune the way they do and do you also do everything else they do? (I haven't heard the recommendation to start young vines in a tube or anything about girdling here so I'm assuming nobody here is doing what the pros do other than training systems.)

The real issue here is that since Trishmick had 8' of upright growth and already cut canes back to the main stem and expected to see fruit this year is that it sounds like Trishmick doesn't know the growth habits of grapes. I would like to find out what the plan is and what exactly has been done to give the proper techniques to suit the desire and get her fruit as early as possible.

Getting back to Trishmick, she (or he) needs to establish a structure that will produce buds for next year's growth, which usually means getting some of this year's growth growing horizontally along a trellis. If Trishmick cuts the top of the trunk off, it will push laterals, but I am not sure if there is enough time for that before the vine shuts down for the winter. Anyway, I here is a good publication about vine growth, training, and pruning (both cane and spur pruning):

I was thinking for cane rather than cutting the 8' of top could be bent over at 5' to force the opposite cane (I learned that in the other thread). I think it should make the extra 12" in zone 7 and that would be one fruiting cane for next year that should be able to produce around 15 clusters (but I would probably go quite a bit less since there isn't a full trellis worth of growth to judge the vigor, like with mine filling their alloted space and more with 2 months of growing left I'm sure mine have plenty of vigor to produce at least a half load and make replacement growth).
If it's a 4' fence that would be plenty of cane length bent over, but in the case of 4' tall I'd probably go with a single T and longer canes.

I don't know if the 8' would be tall enough to bend over for a T cordon and have enough length to fill in for a single cordon to fruit on next year before the growing season is done. I think T type cordon training is taller and longer than Kniffin. I also don't know if fruiting one cordon would take energy away from making a good strong cordon on the other side that would handle fruiting the following year.

But I guess if cordon is desired and it's a tall fence what is there could be bent over, fruited on as a cane and cordons selected out of next year's canes and if fruiting is kept to a minimum they may be strong enough to fruit the following year. I've heard of renewing cordons with no mention of not fruiting when doing it so I don't see what the difference would be other than these are only 3 years old bare root so may lack in vigor somewhat.

That PDF was good. I was having trouble picturing my renewal spurs. Showing them form through the early growing seasons helped.