(still new to the height map stuff so this might be pretty noobish)
First off I know this topic has been touched on in many threads but I can't remember where or what they were so ill just ask again, This has probably been answered somewhere but I just need a little more understanding, Ok the biggest map I've ever made so far has been a 44x44 with my latest Release which is 704m in the editor.....But with each map I build I bring up the size just a bit and with my next map id like to bump it up to a 46x46 which will be 736m in the editor, Problem is I don't really understand what or how the 'KM' on terrain party match up to the 'M' in the editor? Everyone has told me to go full size with the editor map 64X64 for the best results but I've never done a full-size map and I'm kinda pacing myself into daring to do one lol, I'm just trying to get the best most realistic terrain and exactly where to put the KM to match a 736m map...Thanks.

The smallest you height map you can download from terrain.party is 8km x 8km. That's 8000m x 8000m. A 64x64 map in the editor is ~1km x 1km(it's precisely 1.024km x 1.024km actually). So an 8km x 8km height map is going to be ~ 8 times larger than the largest map you can make it the editor. You can use the 8km x 8km height map for any size map in the editor. But the scale won't match the real world. The smaller you make the map in the editor, the worse the scaling will be. 32x32(512m x 512m) would be ~16 times smaller than an 8km x 8km height map.

TL;DR...there's no way to make a map in the editor that is anywhere near realistically in scale with the real world using the smallest height map from terrain.party. UNLESS you crop the height map to a size that matches the size of the map you want to make in the editor. A 1/8 piece of the 8km x 8km height map will be 1km x 1km(1000m x 1000m). Which would be very close in size to a 64x64(1024m x 1024m) map in the editor. So the scale would also be very close to realistic.

Very Helpful , Thanks alot man.