I think you'll be plenty happy with a router/wifi combo. I'm a HUGE fan of having a separate router and WiFi AP's, but that's only because 1) I can afford it, and 2) I'm a nerd and like a bit of a challenge sometimes, and 3) I live in a house and it's beneficial to have multiple access points.

If you want something that will "just work", there are tons of "consumer grade" stuff out there. They aren't necessarily consumer grade because they are bad quality, but it's more the software that is designed to be relatively easy to set up, offering limited options for customized stuff. You'll still be able to do everything you probably want to do, like port forwarding, changing DNS, etc. This includes stuff like Eero, TP Link, etc.

Then you have stuff like MikroTik, which is very affordable but also complex and capable. The hAP series from them are router/wifi combos. They offer a default configuration that will "just work", but from there you can make all sorts of complex configuration changes to your hearts content. Check out The Network Berg on YouTube. One thing to note, people are generally happy with the WiFi from 'Tik devices, but they are not known for having the best WiFi. It'll be stable and work well, but you might not see speeds on par with other brands.

Then you have what you mentioned - OpnSense with other hardware for WiFi. For me, the downsides to this are:

1. Running dedicated hardware just for this is a waste of electricity.
2. Whatever you plan on running it on likely only has 1 ethernet port, so now you're spending money on a networking card. There may be a way to run it using a single eth port, in which case you can ignore this I guess.
3. If you already have a computer on 24/7 for other stuff, you just have reliability to think about. If you have a hardware failure, for me it's faster to replace a router than an entire computer. The likelihood of needing to replace either one is slim, but it's something I consider. Picture this - you update your computer and need to reboot it. It fails to boot after the update and gives you some error messages, but you can't look them up because your router is down.... That sort of thing.

Now back to the pros and cons of having separate router and WiFi AP.

Pros:

1. Can upgrade either one individually
2. Can run multiple APs to extend WiFi coverage
3. Can choose brands based on their reputation. For example (don't take my word on this) MikroTik for router, Unifi for WiFi.
4. Scratches the nerd itch.

Cons:

1. If you use different vendors, you'll have different configuration options to deal with. OpnSense can't configure a TP-Link AP, for example.
2. Adds some complexity. Now you're dealing with more ethernet cable, PoE injectors, and mounting of the AP.

Hope that helps.