Hello Alexander.
I have a group where we analyzed the anti cheats available on the market!
Smart-guard is the best, but there is no support, if you need any help or changes you won't get it.
AA or Active Anti cheat, is very good, it catches most cheats but doesn't protect against paid Adrenaline, which Smart-guard does. It also gives you some bonuses, such as a login save screen and an option to add your server to the discord menu, like Playing L2 Giran Forge.
Strix Guard is the most affordable option out there, it protects just like AA, there aren't many differences, but its updates are few and far between, but its value is very good.
If it's a 100% retail server with no custom interface, Smart-guard is the best option. If it's a server with a custom interface, then the choice is between Strix and AA.
I use Strix, I already have the discord and auto login DLLs, so if it's just to get rid of free and cheaper boots, I prefer Strix.
I hope I helped you!