You can use tstroke or 440 or 640. All works. I've used different javs with same 99fcr set up then did like several hundred chaos runs solo in baal games and I preferred tstroke over any other javs.
Repair every 3 to 4 runs.
I dont know why others prefer 440 over tstroke for pvm but it's preference and im good with it.
It probably depends on the content they are doing. If your 4/40s clear most packs in 1 throw anyways, then the -15 light res from t-strokes is objectively worse (because of overkill) than just hitting the next ias BP.
I've found 4/40s really nice for TZ tombs in particular because you hit the 99 fcr BP and then can throw javs around the rooms quickly with the 56 ias bp. 6/40s would probably feel even better. I still repair my 4/40s every few runs even though they have increased stack size and rep. (Costs like 1 gold)
Maybe t-strokes at a lower ias bp is better for p8 chaos specifically. Ill give them a try.