Praxis BB convertor into 2018 Supersix Evo
From what I understand, you shouldn't have to touch the cables to change the bottom bracket. 

I have used the M30 Praxis BB30 (not your PF30, but similar) without issues. 

Your current bottom bracket shouldn't have issues with the cables and neither should the new one. 

The hollowtech tool won't fit. You have to get their tool. 

As a cheap alternative, you could use mold grips, but this risks damaging the cups, and frankly, it's not worth it. 

If you're not 100% confident, you should take it to a bike shop, you don't have as much room for effor with pressfit bottom brackets, in terms or damaging the frame, incorrect bonding and misalignment.