Are there games like Swat 3 and 4 available or were these the "pinnacle"

If you are asking about tactical shooters in which you have to arrest the suspects, instead of shooting them all on first sight, then SWAT 3 and 4 are indeed the pinnacle, as far as I know, having been a gamer since the late 90s. Of course, I might be wrong, but personally I have never come across any other video game that is just like the ones of the SWAT series.

Ready or Not

Definitely "Ready or Not" but it is still early access and lacks native mod and custom map support yet. People have started to make content for it though.

A lot of the maps are a real challenge to complete with only 2 or 3 players since you don't have control over the number of suspects in the map like you had with Swat 3.

Door Kickers is a great game. It's top down but it's really good.

Door Kickers 2 will be coming here too once early access is finished.

If you like Swat try Arma. Two of them are on here. They're like military simulators with pretty easy to use scenario editors for limitless playablity. Amazing games, you won't regret playing any of them.

Give "No plan B" (Steam) a try. There is a demo available.

It's not that I want to talk it down and I guess you already know what I am about to write, but if any newcomer to the series wants to know SWAT 3 already has the option of having no control over the amount of suspects in the random missions, by just setting the number of suspects and/or civilians as random, which I personally do most of the time. And when you choose multiplayer you can also decide how many squad members you have in your squad, so that you may just want to do the entire mission with just 1 or 2 other players or AI members. The great thing about it is that if you also never check your mission objectives during your play, to find out if they are already fulfilled or not, you will stay cautious until the very last room, not knowing how many suspects the game has given you for the mission. It often gave me a lot of surprises. You can also choose to be a squad member, but not the leader of the team, so that the AI takes control over giving the commands and you can even set up two teams that work together, which is even more fun when one team storms the front door, while the other uses the back door to gain entry. I wonder if Ready Or Not has this as an option?

Nope, hence my comment :)

Another good coop game that people should check out is Ground Branch. You don't arrest the enemies. It is a bit more like old-school Ghost Recon or Rainbow six. You do have total control over number of enemies, time of day.

As for Swat like games there is Bangladesh based developer that has a game called Zero Hour. The weakest link I think with this game is the map designs. It has a lot of potential if you don't mind games not set in "the west".