Expanding the ecosystem from beginner, moving into a rental apartment tips

Hey there, beautiful community. Have been lurking here for a good while and have gotten a lot of answers and inspiration.

I am moving into a decent sized apartment (75 square metres) which I plan to stay at for at least five years or so. I've been wanting to expand my smart home now when I have the possibility to do so, from being a complete beginner just dipping my toes. The devices I have are just some panels of Nanoleaf Elements, an air humidifier from Levoit, Echo Dot 4th Gen and a few Innr lightbulbs.

I've been looking at both Hubitat and Home Assistant (even though HA scares me a bit). I'm looking for a hub that doesn't need to support 120 devices, just to get me a level deeper into the Smart Home wonderland that is compatible with most things and is easy to use. The devices I plan to expand with is mostly lights, sound and some quality of life-additions like automating blinders and such.

Another thing that struck me is that I feel fairly lost in even the choice of WiFi-router, I just want a good, reliable one that I can use even if I move to house in the future. So in short, my questions are:

- In your experience, what is the most important thing that you've learned when starting to expand your ecosystem from beginner and moving in to a medium sized apartment? What were your priorities and what were some common pitfalls?
-Hubitat or HA?

- Any tips on a good reliable WiFi router that might be sustainable in the long term?

Tldr; Moving into a bigger apartment and want to go deeper into SmartHome. Needs tips on ecosystem, experiences and wifi router.