My pi 3 has struggled with some particular codecs or large (greater than 5 hours) videos. I'm not proficient enough to say that it wasn't my fault in some way, some config option, but it was a near thing, regardless. A pi 4 or 5 should do it flawlessly, and my pi 3 works more reliably than my roku, even with that flaw.

WiFi, as long as your router isn't ancient, will be more than enough. Latency isn't a factor, and you can get HD streaming at well under 100 Mbps, the upper limit of most routers. My router, in another room with walls from an old house that destroy my signal, still gives me about 20, which is enough for 1080p.

I will say a pi 3 feels fairly laggy just using it to browse online. It does much better as a streaming box. The pi 5 I just got yesterday is much snappier, feels great to use. The 4gb model is 60$ right now, although I got the 8gb model.

All this was on default raspberry pi OS with kodi installed as an app. Very little to set up besides getting the media itself shared in your preferred way.