We are at the point where there are some TTTF cultivars that have finer blades than some KBG, are equal to KBG, and some wider than KBG. It depends on the cultivar and it also depends on growing circumstances. TTTF widens out when it has room to do so, but stays finer in a dense stand. KBG blade width doesn't vary much in this regard, as an isolated bunch will look like grass in a dense stand.

Brown patch, being a foliar disease, is related to turf density more than anything else. Many of the newer fine bladed cultivars have some of the best brown patch resistance. K-31 is very resistent, but is that related to it's blade width, or another aspect? I'm not sure, but some of the early TTTF's were very susceptible. The turf scientists have really improved on this and I imagine are still working on it today. Brown patch is one of TTTF's biggest problem, and it is the most susceptible cool season grass. TTPR is less susceptible, but it has traditionally had issues with gray leaf spot and dollar spot.

PR is competitive in that it germinates and matures so much faster than anything else. So if you seed PR and KBG together, the PR is up and running in a few weeks, stealing water, sun, and nutrients from KBG which takes longer to germinate, establish and mature. When PR is mature it also suppresses other turf seed germination via allelopathy, thus making overseeding with KBG or TTTF much more difficult.