I'd be cautious about using others as an example of what you could do.

Multiboxing has a very specific requirement in the retail game. It's not Classic and so you need highly mobile specs with great utility that benefits multiboxing. That essentially limits your combos to specific things. Not my idea of fun.

Dual boxing would be my advice to anyone playing Shadowlands, so you'll get your MB itch in the world content and be able to drop one for the harder stuff when the time comes without feeling bad about your investment. Also 2 in PvP is a lot easier to manage than 3.