- 1.5GHz quad core is decent speed - MacBook starts with 1.2GHz dual core (probably faster processor on its own and has 'boost' to 3GHz) but still - not another order of magnitude faster
- 4GB of ram is something older machines (10+ years) couldn't have or was max that could due to architecture (32bit processors and memory management) - many Linux distros worked quite well in 2GB of ram (and much less)
- USB3 (for faster HD/SSD) is faster than spinnable HDs from only 3-4 years ago and more
- 5GHz WiFi/1GBit/s Ethernet - that's quite modern connectivity
I installed raspbian on 'regular' SD card and all pretty much worked (on 350Mbin/s card) attached to 4K monitor. First thing I noticed was that on 3840x2160 mouse wasn't smooth and moved in slightly jerky way. Dropping resolution to 2560x1600 immediately fixed it. That's a bit odd - but my eyesight didn't complain at all
Then I installed my favourite - KDE plasma desktop and it didn't work until I switched 'compositor' off. Immediately but rendered all just fine and the rest of KDE worked as expected (minus fancy translucency and such which I can live without). Speaking of such I suffered a bit with my old Protege (~2004) laptop when it came first (who remembers old composer?!) but now I am not bothered at all - knowing that this is entry level 'desktop' as many say
Next to it installed PyCharm (as I am using it for work on day to day basis) and a few bits like Gimp, Thunderbird, etc...All work at perfectly usable speeds - no significant lag nor something that would otherwise upset me. For all those that suffer from scrolling not being super-smooth (millennial's-speak) they'll be disappointed anyway. But same people complained that VSCode is getting slow even on the fastest MBPs these days...
Speaking of speed - lack of vertical blanking (at current setup) causes a bit of a 'tearing' while moving windows and scrolling of code - but that's something I'm happy to get used to.
Next was to move root partition to some old 80GB SSD (speeds of ~2GBit/s through old USB3-SATA caddy), set it up to boot from there and I/O become more than reasonable (definitively better than old computers with spinnable HDs) and responsivenes of system returned to what we all got used to.