Welcome!
I compete with a standard (i.e. non-SSR) 686, mostly IDPA, some ICORE and USPSA (our version of IPSC). It's a fine gun for IDPA & ICORE, and I have done ok with it in USPSA as well. I'll likely switch to a moonclipped .45acp 625 at some point for USPSA, though.
The SSR looks like a fine gun. IIRC, it comes with an interchangeable sight, so if I were to buy one, I'd just exchange the factory front sight with a fiber optic, then go shoot some matches with it.
With my 686, I use a BladeTech holster.
ReadyTac also makes a good kydex holster. For USPSA/IPSC, a
CR speed holster seems a popular choice, too.
As far as speedloaders, I use
JetLoaders, but
Safariland CompIIIs are very popular too.
I use
ReadyTac's speedloader holders, and are very popular.
BladeTech holders are popular as well, and I've seen
Safariland 333 holders in ICORE/USPSA matches.