2 GB is enough for most devices. A Raspberry Pi 4B set should be fine. FYI, Kodi itself offers no streams.
Just a heads-up: should you be referring to streams that offer the latest movies and tv series, then you'll have to find your support elsewhere.
"No problems" is an impossible situation. Nobody can promise that there won't be a problem at some point.
RPi3B+ is even cheaper, and can play 1080p. Installation is pretty easy on microSD.
Expansive box: no problems
Cheap box: problems (but support is right here 
)
Pi 3B+ and 4B 2GB seem to be the same or similar price. I just upgraded my 3B to a 3B+, because I don't need the 4B's extra grunt at this time, and save myself a fair bit of money because I don't need to buy a new power supply and case. If I were to start from scratch I would pick the Raspberry Pi 4B 2GB as the "cheapest" viable option, at least for LibreELEC. Support is good and I'd say it's almost a turnkey solution.
We had the discussion about cheap China boxes a couple of times. Specs sound good, but they usually have a locked bootloader. A locked bootloader is a problem, because the OS can (if even possible) only run from an external device (USB stick). It's no easy installation by the way.
Tell us what you wish to play on LE, so we can avoid that you double-dip boxes (not cheap anymore).
If I were to start from scratch I would pick the Raspberry Pi 4B 2GB as the "cheapest" viable option, at least for LibreELEC. Support is good and I'd say it's almost a turnkey solution.
Can Pi 4B 2GB handle 4k contents well ?
Can Pi 4B 2GB handle 4k contents well ?
Handle well... 4K of what? h265/hevc: yes, h264: no, vp9: no, HDR: should do now.
What kind of 4K are you looking for?
Handle well... 4K of what? h265/hevc: yes, h264: no, vp9: no, HDR: should do now.
What kind of 4K are you looking for?
4K h265/HEVC SDR, HDR to SDR Tone Mapping as I'm using 4K SDR monitor now
4K HDR passthrough as I may get a 4K HDR TV in future.
Thanks
