From one SRF Noob to another you've made the right move! I made the jump last year and also came from the ITA/SM community.
Competition may be a little tougher. Most of the SRF drivers have been driving and driving this car for quite a while and are very good at it. Now is a good time to make the move as the gen 3 upgrade and new tires have leveled the playing field a little.
That said it is a true spec class and if you have good driving skills but haven't been creative with the rules or pushed the umm...................grey areas in SM/ITA you'll probably do better in SRF. If you're used to paying for performance over there life might be a little tougher here.
As for equipment the previously mentioned visor advice is spot on and important. I also feel a butler seat and the new head restraint should be added to your list. Most driving coaches/books will tell you a drivers seat is the single most important investment you can make. Not only will it help you go faster but it'll make you safer.
In my very first race I was launched into the tire wall. The car went onto both sides and both the front and rear impacted the wall. The next day I was driving again with no issues. I'm fairly certain that wouldn't have happened without the butler seat and head restraint.
Handling is different. If you PM me I'll give you a couple more pointers as I don't want to give to much away in a public forum. My 1.6 used to be setup so that I had to be on the gas to balance the car. If you've ever setup that way it feels similar but for different reasons. While the car isn't as forgiving as the miata it's way more rewarding when you get it right. The overall fun factor from the increased performance and open cockpit are awesome as well.
I've owned 4 miatas..............wow can't believe I actually admitted that.
The car is every bit as reliable and tough however like the miata has a couple of minor issues. If you go off the track don't spin your tires as you come back on as that will sometimes break an axle. DON'T bump draft and be very careful when following someone. In miata's we were really used to the occasional bonk or bump drafting. Here that'll usually mean repairing the nose and maybe getting an opportunity to fill/flush and replace your radiator.
If you do you're own work you're really in for a treat. This car is soooo much easier to work on. I haven't found anything yet that isn't easier. If you don't even better as the CSR's are at pretty much every event and are really great to work with.
Welcome to the class, you're really going to like it!