Do MS2020 and 2024 have AI? Carrier ops? Assume my faithful T-tools and other old sim utilities are useless.
MSFS and MSFS2024 have AI, but I'm not sure if you can get anything as "precise" as the P3D AI packages, in freeware. You can definitely get the world populated by AI aircraft from real airlines with real routes, but I have not investigated this aspect that much yet, so I'll let the others give more details about the products that exists, in freeware or payware. Indeed your old tools are now useless (you might want to keep an eye on JoinFS, maybe... but the native multiplayer is already quite nice and very easy to use).
Carrier ops exists and are very nice, on par or better than in P3D. Some tools exist to interact with a carrier and command a few of its elements such as elevators and jet-blast doors, but I recon TacPack was offering much more options for this, especially when it comes to multplayer... Be aware that you'll have to install addons (freeware or payware) to get moving carriers around the world. By default, there are a few carriers here and there but they do not move, if I'm not mistaken...
Here is an example of freeware:
https://flightsim.to/file/35879/moving-aircraft-carrier-with-lso-arresting-cables-and-catapults
And payware:
https://miltechsimulations.com/products/supercarrier-pro-for-msfs
In addition to carrier ops, you also get a very nice aerial refuelling with a connecting basket/boom and flexible tube etc... by using the payware version of a tool called "Airshow Assistant" (which has a freeware version too, but that one doesn't contain the aerial refueling). You can call a tanker (several choices of models included), define its cruise speed, choose the difficulty level (easy = the basket will move by itself to reach your refueling probe, hard = no help), you can break the tube with the basket remaining attached on your probe, and you get audio and visual guidance as expected. I highly recommend it to you. I was frustated by the absence of this feature during my FSX and P3D years, and I'm very glad to finally enjoy it in MSFS without having to jump into DCS.
Finally, a bit of warning: I see you are not decided yet on choosing MSFS or MSFS2024.
I would recommend MSFS2024, but the thing is that not all of MSFS addons are compatible with MSFS2024 yet.
Still, I can't recommend you to spend money on MSFS now, it would't really be a wise choice...