Welcome to our forum.
I am a HS dealer. Provided the 20 and 30 amp breakers you use are GFCI's, you CAN use the box you've got installed. It will not affect the warranty on the spa. However, I would put the Hotspring box in. Here's why:If you have a breaker trip and the technician comes out and says you have a bad breaker, it's not ours (Hotspring), and you need to get an electrician out to change it, you will:1) Pay for the spa technician to diagnose the problem2) Pay for the electrician to replace the breakerIf you use the Hotspring box, the spa tech will have the correct breakers on his truck and, in such a situation, you'd be back up and running at no cost (since the breakers are covered under warranty). You paid for the warranty on those breakers. I would advise you to take advantage of it, even if it costs a little to change it out.Enjoy the Vanguard - It's awesome!