Hi all, This is my 1st post, so be gentle!
I'm currently testing Bodhi 5.0.1 (non-HWE) with intentions of using it to replace Windoze-10 (don't really have to try too hard!), but have come up against a few small issues with font sizes. I'm using a 28" 4k monitor (3840x2160 native) but I'm finding the font sizes way too small to read for extended periods! I have already set my scaling to 1.2 (Settings-->Look-->Scaling-->Scale Settings, Policy shows Custom scaling factor = 1.20x with Base DPI - Currently 157 DPI), which helped a lot, but the Font size on the iBar/Panel is still VERY small. This also makes the main menu hard to navigate with mouse as even the slightest movement too far up/down changes the category pop-out menus & it's driving me nuts! I did install the Engage module to give me an application Dock-Bar (as Docky & Plank were no good to me as they don't seem to 100% compatible with Moksha - could not get the docks to auto-hide when other windows overlapped them no matter which options I choose!) BUT as good as the Engage-Dock is, it also has a font/text issue in that when I move my mouse over any Application icon (on the dock) only the 1st one or two characters pops-up, no matter what Engage settings I change (zoom factor/zoom disable, etc does not improve things). Otherwise I'm 100% loving Bodhi (especially as my PC only seems to work with about 3 x ubuntu/debian distros, & I've tried about 20+ so far - ALL of the others give me a blank/black screen with flashing cursor in top left of screen on 1st reboot after clean/new install)
Many thanks for any pointers on how I may try to resolve these issues.
PS. I have screenshots that show my issues more clearly but not sure how to attach images to forum posts.

Seems like you're playing with the right things. I use a 17" 1920x1080 and have scale factor set to 1.6. Some things, like the start menu and moksha settings seem to ONLY be affected by the scale factor, where other things seem affected by font sizes/etc. So if nobody offers better advice, I'd suggest increasing your scale factor to make moksha/menu good then trying to decrease other stuff that's too big after that - resize your shelf etc after finding good scale factor for menu/etc... One of the bodhi devs recently recommended installing lxappearance to control gtk stuff (which I've never tried...) - but still get a good scale factor first!

yes, I have had moderate success by increasing my scale factor to 1.6. And yes, you're right about this only affecting certain GUI aspects of the OS. Some Apps are affected by the
scale increase, but others remain extremely small! For example PCManFM is nice a big now, but the system-monitor fonts are tiny! Web-Browsers are also affected in that I can increase
the webpage zoom settings (either all elements or just Fonts) but all the Menus/Icons remain so small it's almost impossible to read! This happens with Firefox, Opera, Eolie, Brave
& Slimjet. Incidentally, I have also noticed that if I increase the mouse pointer size, the pointer will DECREASE in size as I move it over certain open App windows. The pointer
stays large when the mouse is over desktop or navigating the main-menu or if I move it over any App that respects the scaling (like PCManFM, terminology) but drops to the smaller
scale pointer when pointer is over any of the Web-Browsers mentioned. It appears that maybe this pointer issue directly links to the tiny App text/menus problem, except for a few
exceptions (like system-monitor, which has tiny text but the pointer does NOT get smaller when over the system-monitor window!!?)
I know from my experience with Windoze10 & Hi-DPI (esp. 4k) monitors that getting fonts/icons/menus to work correctly can be a very frustrating experience! Again, it would seem that
unless the Apps have been specifically written to take account of Hi-DPI screens, you have to start tweaking the individual App's advanced settings to override what Windoze will try to
do due to your custom OS scaling settings. Some other versions of Linux I have tried have better Hi-DPI screen support than others.

Yeah this has something to do with what the app was designed for. Apps designed with GTK (gnome tool kit) and aren't affected by the mosksha settings. I think thats what lxappearance is for. install and run it and try. Same thing with the mouse pointer in GTK apps.