I was lucky since I converted my pool a year ago with Circupool RJ 30+. One less thing to worry about with this virus stuff. The 40 is the right size for you. TFP recommends size the chlorinator for 2x your pool size minimum. So if you want to go larger no problem!
Here's a link to a great brand comparison page. I'd look hard at the sale that allows you to buy an RJ 20 and get a 45 for one $ more.
If you do it yourself you're looking at about $1000 plus incidentals. Installation was a breeze! Just wire it so it gets power from the same place that powers your pump. Circupool was great to work with, superb customer support and their warranty was the best I could find. I looked at all brands and chose them based on $/lb chlorine production, warranty for DIY, and reputation here. There were a couple that were close on this basis. Tie breaker was a lot of satisfied owners here.
When you order your swg order a K-1766 salt test kit at Amazon or other online supplier. It's about $20, easiest drop test you can do, the most accurate test you can get, and has enough reagent to last for years. You need to measure salt before you add salt. You'll be amazed at how much salt is in the pool already probably around 1000 ppm. Most don't realize they have a salt pool already!
Once you decide you want to try it and if you have somebody in your family that you're afraid won't like it add the salt and let them try it. My wife did this and immediately loved it. I chlorinated with liquid chlorine 'till I got the unit installed. She'll never let me go back.
There are lots of threads on here about installation. And ask any questions you may have here since we sell nothing... just want to help and we have
real experts. Beware of any advice you get from somebody that's selling you something.
Good luck!
Chris