if i want a new shoot to get as strong as possible, does it help to pinch other shoots so the energy goes to the one i have?
No, it won't help and will do the opposite. When you prune back a branch, it's hormones etc. go into overdrive and trying to reproduce what was cut, often coming back with two new branches. If anything, wait til your 'weaker' one has a few good pairs of leaves on it (~6) and then pinch it back to a couple of pairs, it may not fatten up appreciably (until later in life) but will put out more foliage.
The advice I've received, on pruning branches, from Atlanta Bonsai Society workshops, is:
The best way for a branch to become stronger (thicker diameter) is to let it grow unpruned, and prune out other competing, undesired branches, so that light and air can penetrate to the desired branch. If you want to keep a branch from getting too thick, keep pinching it back.
(this is from the Kenji Miyata and Tom Nagatoshi workshops March and April this year)
Your advice to hatflyer seems to be the opposite of that, and has gotten me confused. Which one is the correct method?
Kenji, specifically, in his workshop, kept talking about 'sacrifice' branches - unneeded branches left on the tree to thicken the trunk, and then removed when the trunk attained the desired thickness.
Thanks in advance for the clarification.