My guess is that it won't be long before you are starting to plan that custom bike based on what you *really* want it to do.
That is one of the reasons I came here more than a decade ago, because I didn't know anything really, even though I used regular bicycles for everything, and knew electronics, I was just beginning to learn about batteries and motors and such, and I am still learning things every day to pass on to others as I can.
When you do start planning... sit down and define and prioritize exactly what job the bike has to do for you, and under what specific riding conditions for what kind of distance/time, and what features you would like it to have, how you would like it to respond to you, via what kind of control inputs, and what you would like to happen in various circumstances as you use those inputs, what kind of customizability you would like to have in how it operates, etc.
And how much you are willing to spend for all of that, as it may not be cheap.
That will let you choose a controller system that has at least most of the features you want (probably none have everything at once), and is powerful enough to do what it has to do for you.
Then you can find a motor that supports the power / etc the job requires, and a battery that can supply all the power to do that for the distance / time you need it to, and last the lifespan (years/etc) you need it to before replacing it.
Then find or make a bike frame/etc that can carry all that and still do the job and be the kind of bike (probably motorcycle) you want it to be.
I've spent some years doing this experimentally, incrementally, but if I had sat down to do this originally, I could have probably had what I needed much earlier. :lol: