FVTM is a pack based mod, with which you can add content to the game without any Java knowledge! All with fairly simple config files. Among other you can create:

vehicles, drive-able vehicles (land and rail, other types wip)
parts, to customize your vehicles
- wheels in varying sizes and with varying terrain attributes
materials, generic items which you can use in recipes
consumables, custom food and drinks
blocks, basic blocks, rotated blocks, animated blocks, blocks with functions, blocks with inventories
multi-blocks, customizable machines
clothes, custom wearable armor items

Supported Model Formats:

JSON (only for blocks and items)
OBJ (including blocks and clothes!)
FMF (model format exported from FMT)
SMP Toolbox models (uncompiled!)

Other Cool Features:

legendary road tool (see YouTube video) or bilibili

Content and Pack availability!

Depending on Minecraft version, not all features may be available to the same extent.
Packs are version neutral. You can use FVTM v4 packs on any version FVTM v4 is available on!
But unless a pack for example was specifically updated for 1.21, you may experience things like missing item icons.