Welcome to the boards, angelicskull! (And a Feinberg quote? What a treat.)
So, what feels good to someone with any kind of sex -- including any kinds where something of your body is engaging with an orifice of theirs* -- often won't be the same from person to person, so the idea that we need to develop physical skills to make us "good" at this or any other kind of sex is, I think, a little bit misguided and certainly something you don't need to worry about.
The real skills to develop when it comes to sex with other people are skills of communication: learning to listen, to talk openly about sex, to be responsive to what a partner is telling us (and to learn to respond well, including when what they tell us may make us feel uncomfortable, insecure or intimidated), to be someone they feel comfortable being honest with, to learn how to communicate well before, during and after sexual activities. Those are things we can work on outside a relationship or interaction, but again, they're also pretty bespoke for who the people involved are, so that's mostly stuff we work on together once there's an actual person involved.
In terms of the physicality of things, this sounds a little to me like something you might be overthinking due to lack of experience? Again, bodies are all so different, so something like how it works to be on top of someone is going to be something you figure out based on how your body and another person's unique body are together: these are things we learn with practice as we get to know each other's bodies over time. I also would not say that strapping on involves a lot of weight at all: most harnesses are very light and the same is true with most dildos. If you're concerned about stamina during sexual activity, that's something where the kind of basic physical activity suggested for all people for general health should do you just fine. On top of all that, you're a drummer: I'm sure you get more than enough conditioning with your hands from that much-more-demanding activity to be able to do things with your hands a partner might enjoy.
Are you seeing someone or generally dating? Is any of this something that's actually likely to be in your immediate future, or for right now, is this all pretty intellectual?
* I don't use the term penetration/penetrate in my own sex life or in my sex ed work for a lot of reasons, one of the biggest being that it gives people the idea that orifices and a person with an orifice something is going inside of are passive, when instead, both are (and should be) very active: orifices are tubes of active muscle, after all! Aside of it also always feeling like a much better word to describe sexual assault than consensual sex (penetrate means "to pierce" which isn't generally how these kinds of sex will feel to either party when it's consensual and wanted and everyone's bodies are turned on), it just seems to be to give people an idea about this kind of sex and how it works that doesn't support these kinds of sex actually being as good as they can for everyone involved. <3
. i know my first time is going to be awkward no matter what, but i want to be okay enough at it i guess.