Ball fittings are posted in the fittings area at the homepage of Titleist.com . There are also virtual fittings available to talk to a Titleist fitter. After the discussion, typically they will send you 2 - 2 ball sleeves of A and B choice balls from the call.
I would guess outdoor fittings won’t be available in your area until April. Personally, if I had the option for an indoor fitting I would pass as the ball flight is not a true window.
Whether they send you 2 balls or you buy a sleeve or a box, it may take you 2-3 rounds to see which is preferred. Hopefully on a day w/o pace of play pressure to take paired shots to see the windows off of various clubs.

Hi Brian! Honestly, if you’ve got it narrowed down to V1 and V1x, then this is an experiment you can undertake yourself. Start with a sleeve of each at the short game area and just make sure that they both work for you from a feel perspective. Personally, I’ve found that from 50 yards and in all the ProV1 variants perform extremely similar, but some are more sensitive to feel than others.
Once you’ve established that the short game feel is good, then as Don said, it’s time to hit the course. Find a day and time (usually late evenings work best) that the front nine isn’t busy and play two shots from every position. You should find relatively quickly what ball tends to get you closer to the hole. Focus more on the iron shots with an emphasis on 8-W. From there you can modify your driver with the help of a launch monitor to fit the ball that works with your scoring clubs best. Good luck!

Brian, I am also thinking of moving from the Pro V1 to the Pro V1x. With some swing work this past year I am swinging a bit shallower and a better impact. I have been doing the task of playing on the course and hitting both balls off the tee and then hitting both from one of the positions in the fairway.

For me both ball are similar off the tee and long Irons. The real tell will be short Irons and chipping.

Happy Testing!!

You should go to a good fitter, look at the launch numbers before you do anything. It's great to try to compare for yourself, but Trackman data will show you the optimum launch/spin vs your clubhead speed. Higher compression X's aren't quite as soft feeling as the regular ProV1, IMO. Also depends on the irons you're hitting, forged vs cast. Alot of variables involved. Good luck!