About 10 years ago I shot IDPA semi regularly.
I never was great at anything but I had fun and started getting better (very slowly).  At the time I shot everything with a 1911 in CDP.  I used a Galco Royal Guard IWB holster setup (this was one of the recommended setups for people who were afraid of Glocks back then).  Then life happened and I stopped.

I've decided to get back into it, and I think maybe I now have the necessary time and resources to take it a little more seriously.  But at this point I'm still basically a beginner.

The last 2 recent matches I shot with a full size Sig 220 (elite w/srt), and the one before that I shot with a USPc (world's worst trigger and 357sig.  despite being a ridiculous caliber I still did okay with it).
Inexplicably, I feel more confident with the DA/SAs than the 1911, and I seem to consistently do better with them.  At this point I'm looking for gear recommendations.

Assuming I stick with the Sig220, what holster setup would you recommend?  Right now I have this leather paddle with a thumb break that seems horrible for IDPA.

Alternatively, I'm sorta open to suggestions for something else.  I could get a .40 barrel for that HK and one of those grayguns trigger upgrades, but then if I'm spending $500 anyway, why not look at a Sig226 or even a CZ-75 or something?

TL;DR:  What IDPA holster for a fullsize Sig220R?  If a Sig220 is a stupid idea for IDPA, what other non-striker-fired platform would you recommend and why?

Welcome (again)!

From what I have seen - the local matches are very much whatever you want to shoot and with whatever gear you can safely use.  We seen IWB alien gear holsters, OWB carry holsters, competitive holsters.  Guns are all over the map.  Lots of guys experiment at the local matches with all sorts of random guns they have holsters for.  Safety is still the ultra paramount item - as long as you are safe and the gun is safe, run it.

The bread and butter of OWB type "IDPA" holsters are Comptac and Bladetech.  I would start there and have a look around.  I am positive one or both of those companies will have something to fit your needs.
Mag carriers are the same - Comptac and Bladetech are great options.

The Sig p220 is a great gun. You'll have a DA first shot which others in CDP likely won't have because they have 1911s, but it won't hold you back.

Look at Comp-Tac, Bladetech, or if you have 30 days to wait, Red Hill Tactical makes the best competition holster I've ever used and I highly recommend them.

A new gun might be fun. The CZ SP01 with a safety makes for a great IDPA gun, you can shoot it in SSP with DA/SA or SA in ESP cocked and locked. The all steel frame brings you right up to the max weight and they have a good trigger and decent sights out of the box and are very upgradable should you want to.

Thanks.  Oddly enough I do better with the DA/SA than the 1911.  I think I somehow developed a bad habit of jerking (rather than squeezing) the trigger on a 1911 and the DA/SAs helped me overcome that habit.

Just shot another match this morning.  Screwed up a few stages early on and did pretty well IMO toward the end as I settled down.  I'm about to order a new holster.  Based on the recommendations above I'd like to go with red hill tactical as a first choice, but i have no real idea which attachment option to go with.  Any suggestions?

ETA:  Bladetech, ELS, QLS short vs long?  I'm not sure what the differences are and I've no idea which one to specify.  I'm using the comptac kydex reinforced 1.5" leather belt if that matters.

Oddly enough I am also looking to try the support with my Sig P220 Elite. QLS are designed to attach holsters to belt where ELS are designed for attaching gear to a belt. I am using a Safariland ALS holster with ELS attachment on a 5.11 1.5" belt. The mag pouches are also Safariland and are mounted with ELS. I did this so if I continue in the sport and upgrade the belt I can use the same gear. Like you I feel much more comfortable with a DA/SA pistol then an 1911. If I were to go to a 9mm, I was thinking. Of using a Sig X-5P320. The gun seems to be ready out of the box for competing in pistol challenges. It comes with four magazines and Sig has a $50 promotion off web store gear also.