I have only played the Season 1 PSOne game. I hear that the GBC game is horrendous and to be avoided. Which given its Chibi nature, I probably would have at the time, even if I had ever seen it.
Your assessment of the game, just from watching it, isn't wrong.
The IntroFor any that haven't seen it, please click above for the games intro... The VO for this game has to be heard to be believed, especially Rhinox
When I played it, it has the same difficulty curve as the PS2 "Armada" game IE It's hard and you need to
Git Gud fast. Yet I too felt, if it was properly finished, there was a good game underneath the poor exterior. I even took some of it's extended lore to heart with my own work.
As with any game with a large roster, some of them will never be used. Maximals, you use Primal or Rhinox. Predacons, you use Megatron or Inferno. Although it has been many years since I've touched the game I remember Scorponok and Rattrap should be avoided at all costs. Ironic, given that Rattrap is an unlockable character (in-game lore: Rattrap came after Airazor and Inferno
).
A shame that no other Transformers game I've played has given you the immediate option of Factions from the outset. The rescue missions were an interesting idea also. When a character died, which happened a lot, finish the level with someone else and your respective Faction Fliers had an on-rails arcade shooter mission to free them. Which opened up the roster to Waspinator, Terrorsaur and Airazor. Although they didn't have Beast Modes.
Most of the game was bad however, but it did have some good ideas.
As for the Transmetals game, I never heard of it til way after the N64 era. I don't even think it was released here in the UK and if it was, it had zero fanfare.