No judgement meant, but without understanding your use case it's hard to make a good recommendation.
What you asked first: I have an Asus Ally X. I'm truly just like @strayce@Strayce@lemmy.sdf.org in that my purchase choice was influenced by the ability to use it with an eGPU. From what I've read, using an AMD eGPU with an Ally X is a recipe for frustration, but Nvidia eGPUs are fine. I never actually pulled the plug as my use case for the device changed after I started using it. It can absolutely be used as a full fledged PC, since it actually is one, and I've taken advantage of that a few times.
Musings on my pursuit of a convenient single device solution follow. You're welcome to stop here. I'm not here to try to convince you of anything, only to share my own struggles. Maybe you'll even be able to help me with them.
I've been chasing the promise of a convenient all-in-one device for a while now. Tablet form factor devices (surface pro, iPad, etc) are good as tablets, but propping them up on your lap with a keyboard is awkward. I've found that this limits where you can realistically use them. Sure, you can use a tray/lap table setup, but if you need to haul it around with you it starts to lose convenience. I've always fallen back to using these devices as tablets. It seems like using a handheld as a computer replacement would face the same hurdles when you're away from your desk and add another one: the need for an an external display.
As for why I didn't buy an eGPU for the Ally X, the most frequent time and place I use the Ally X is on the couch, next to my spouse as they watch TV, after my kids are asleep. I quickly realized I was self-selecting which games I play on it. I'm actively avoiding entire genres like real time strategy, which I personally enjoy a lot, because those games greatly benefit from a mouse/keyboard setup. I want a fast/convenient setup and break down. I don't want to have to worry about gathering and stashing accessories. There's also the reality of running on battery and heat dissipation. Keeping the Ally X in 13 watt "silent" mode results in 20 watts of actual power draw, very low fan noise, and ~4 hours of battery life. Its 17 watt "performance" mode is still fairly quiet and lowers battery life to ~3 hours. My spouse finds turbo mode too loud and you're looking at 1.5 hours of battery life. Noise aside, playing while plugged in diminishes the convenience for me.
Despite a few false starts, I've still found myself stuck in the camp of portable device + laptop + desktop - although my desktop sees pretty infrequent use these days.