I am roughly your age and went from USATT 900 3 years ago to USATT 1400 right now. My experiences:
* I first played inverted f/h and b/h and learned a decent f/h top spin and a so/so b/h top spin. This is the combination most people play against most of the time so no surprise, and physical conditioning matters to some degree. So am mostly losing against really well coached little kids, teenagers, college students, and mature players under 40, or under 70 with experience.
* I then wanted to copy Mima Ito since she has a physical disadvantage and still wins against double inverted players (most of them). So I got the Nittaku Moristo SP short pips and the FastArc G1 (f/h) on a 7-ply blade (Yinhe 437). Worked pretty well against little kids and teenagers, and to some extent older players. I then got the Yinhe Uranus Pro short pips which are more forgiving and do have some spin (medium sponge, soft sponge is more finicky).
So pretty good, I got to maybe USATT 1300 but I lost against other pips players because with the short pips you can't put much spin in the game and my twiddling wasn't good enough and required 2x the training time - 2 sets of strokes.
* So I went back to double inverted for a year and made it to USATT 1400 but plateaued there.
* After the Nationals, 4 weeks ago, I concluded that I am better off with long pips because I was beaten by 70+ experienced players with short pips / long pips combination and they didn't exert nearly as much effort as I did. I started with a too fast blade and Curl P3V pips which are good (with 1mm sponge), and this went pretty well. Then I switched back to my slowest blade (Victas Swat) and this went even better. I tried other long pips (Neottec Tokkan), Sword Venom 1mm, Dawei 388D-1 0.8mm, and also medium pips Dawei 388-C1-1.3mm. I found that the pips all are roughly the same for me. I watched the "Lange Noppen" videos on YouTube (by Sebastian Sauer et al.) and some other ones. I played a tournament 4 weeks after starting long pips and went up 50 points or so but overall I played my better and closer against people who had destroyed me earlier, including long and short pips players.
I also want to say that I had a coach through the pandemic 2 hours/week and right now I can play 2 hours/day on a machine or with collegues who are mostly better than me.
Also I did play competitively in my teenage years where there was a lot of diversity in the table tennis styles (no YouTube) and so I do understand spin variations, antitop, long pips, etc.
Key points:
* Slow racket, not fast racket
* Keep long pips on the backhand initially, find out early whether to play OX (no sponge) or 1mm sponge.
* Watch Sauer YT videos and learn the long pips specific techniques (Druckschupf, Hackblock, Nopspin ;-).
* Need 2 hours/day on a machine to get used to the rubbers within 4 weeks or so.
Good luck !!