Starting with the Monster modes, and one thing that I find interesting with them is that once their original Cold Spark gimmick was removed, these guys do not a very cohesive team, with the only thing connecting them together (other than shared engineering) is that they're all monsters of questionable design. You have Twinferno that turns into a two-headed dragon, Grotusque that turns into... a purple and grey naked mole rat with wings and a dragon tail... and Repugnus that turns into one of the stupidest looking bugs that I have ever seen. I honestly love Repugnus' alternate mode the most because of how undeniably stupid it is, while still being sincere about it, like the other two are trying to be scary monsters, while he's just happy to be along for the ride. Twinferno's problems can be identified here already, as I wish the dragon necks had more movement in them. While they are ok in dragon mode, robot mode becomes more of an issue. I am honestly surprised no one has made an upgrade kit to give this thing better dragon necks. As what was standard in the line, all of them come with a Titan Master to act as their robot mode heads, and the robot mode weapons can become seats for the Titan Masters. However, a problem I had with the line, something that became worse the further along the line went, was that the deluxe class guns do not have somewhere to mount onto the bases in a nice way, a central post that could plug into the bases to act as the turret. Repugnus' swords are actually the worst offender of this as there is nothing to do with them once they are in Titan Master Seat mode.
Onto the robot modes, and while they all look ok, they rather loose their appeal here, and look generic save for the odd bits of kibble. I think these three best describe my views on the G1 beastformers, because while they could have great alternate modes, a lot of them especially in the post movie characters, loose much of what made them interesting when in robot mode. I think the worst of them is probably Twinferno, mostly because of those arms. I hate Transformers that make me have to choose between holding the guns in the right way (cannot really say hands cause here the dragon heads are the hands), and having an elbow joint, and all that would have been needed is a small swivel at the dragonheads. Grotusque, though more generic, is the clear standout between the two, but not for being anything exciting, more so just not doing the basics worse. Repugnus is the worst when it comes to the generic look, because with the exception of the bug arms becoming noticeable robot pecks, he is extremely basic. If you got the Titan Master version of Repugnus, you can replace the titan master with it, giving him larger, more noticeable eyes (which I personally think looks better.
The Monsterbots are kind of like the Autobot and Decepticon clones in terms of relevance now, but they also have the added issue of no longer having the gimmick they were known for. While it is nice to have representations of them now, the modern age, is not kind to them, due to them falling into the generic category, existing for a gimmick, and nothing more? What do you do with them now? They are a good novelty piece, but until someone does something interesting with them, that is all they will be, a novelty.