Hey Welcome DrB,
Yeah there are a number of great tools out there - and a paradox.
Blender.org is my favorite - but it is massive (as you probably know).
Paint3d (never used it)
POLY -looks cool (maybe just a market place like sketchfab):
They used to have a low-poly editor, it looked nice.
Babylon was being used behind the scenes for an - anyone can create 3d app about a year ago.
Remix3D. 
There is houdini. 3DSMax Maya…
And sculptiris… is pretty EASY. Probably worth a look.
BUT … editing in babylon eventually becomes faster than Blender .
For some things it is better to edit directly in BABYLON… right?
AND what is on this side and that - of the grey line grows every day.
For example I create 10KeyEditor to edit in BABYLON RUNTIME.
A bunch of us are creating custom editors. The BABYLON.Gizmo is a good example of that coming to full potential.
For your requirements - maybe sculptris. But I’m sure others have great ideas too. Also dug up this…
https://www.sketchup.com/plans-and-pricing/sketchup-free
