I am using a 8 MOA standard railway, polymer and standard switch., I don't believe you need the tactical. The switch is up to you, and as far as polymer or aluminum I find no need for aluminum in this instance.
I have always had a question about this- PCC is now a division of USPSA right? If you are paying match fees for a sanctioned uspsa event how can they dictate what divisions are allowed and not allowed. If its a official division and you are shooting a USPSA match shouldn't all divisions be allowed?
The only downside to SBR would be if you shoot matches out of state. While I am not the most versed on the laws regarding it don't you have to file paperwork while transporting a nfa item to another state?
I have a Dawson CRP edge that I might be thinking about getting rid of. Shot PCC for the first time and not sure how much my limited gun will get used next year now.
Ill address one part of the question regarding the thermal dissipator- don't bother. I highly doubt you will be shooting the gun fast enough to notice any difference.
I cut back on other hobbies to have more to spend on shooting. This year hasn't been that bad besides buying a few new guns. Reloading supplies were stocked up besides primers from last year, out of the 3 or 4 matches I shoot a month I usually only have to pay for 1-2 of them. I just started getting into 3 gun and bought a PCC so its time to stock up on some other reloading supplies.
Ive heard this phrase said a bunch recently- buy once cry once.
Go with JP (I just bought a gmr-13 myself), you will not be disappointed.
With that said I bought the gmr strictly for PCC, I will continue to shoot my 5.56 for 3 gun.
Not sure on your price point but I have a JP and love it.
another option is I know PSA makes a glock dedicated lower when you can find them. Build off of that