Consider the example of General Rahm Kota. I've always preferred the explanation that clones are the frontline fighting force, and for every one of them is a thousand Just Some Guy doing backline duty, crewing ships, etc. The Kaminoans only have so much space on their shitty water world, and it can't be easy or cheap to feed quadrillions of men while you're kicking your heels waiting for the war to start.
Unless of course, you're being funded by the space equivalent of the Rothschilds, which Darth Tyranus and Darth Plagueis were. Palpatine had the former as his apprentice, and he killed the latter and inherited his wealth. They were also wealthy enough to buy a galactic invasion fleet to ferry the Clone Army to hotspots all over the galaxy, and I assume that would be far more costly than any number of clones, especially when these ships numbered in the millions since they had millions of worlds to patrol.
There's also the fact that the clones being the cannon fodder is their basic duty, which is the main point of the story for the Republic side of the Clone Wars. They're the expendable schmucks that Palpatine sent into the jaws of hell so that random Joe the Republic citizen doesn't get drafted for the war. After all, if the Republic starts drafting people for the war, and they come back home in body bags, Palpatine's going to lose popularity points, and no would-be dictator wants that; he needs the people on his side when he starts ripping the Constitution apart and making himself king of the galaxy.
Anyways, it was the droids that numbered in the quintillions, not the clones. Hence why Palpatine had to end the war in year three. Otherwise, the sheer number of the droids would eventually wear down the clones if the war goes on for 5-10 years. Even if they draft entire population sectors, it would eventually come up short. At most, the clones probably numbered in the billions, maybe even low trillions.
The only reason the CIS didn't steamroll the Republic in the war, outside of Dooku pulling his punches, is also because the Republic had superior warships. Sure, the Providence-class is a great warship, but most Confederate ships are Munificient and Lucrehulk-class ships that are basically cargo and communications ships with guns slapped on them. The former are not known for being able to stand up to even outdated dreadnought-class heavy cruisers in a 1v1 fight, and the latter can get flattened by two Acclamator-class Troop Transports, as was shown in the Republic Commando game where a Lucrehulk got destroyed because it chose to stand its ground against two of those aforementioned Acclamators. They aren't even the strongest ships the Republic fielded during the war; the Venator and Imperator-class Star Destroyers far eclipsed the Acclamators in firepower and tonnage.
It doesn't matter if you swarm a planet with billions or trillions of battle droids if the enemy fleet won control of space; they can just pull a Darth Malak and glass the planet, killing your droids. Or bomb enough of it so that the Clone Army can swoop down and take the planet.
Can someone please explain the Nihil from the gay high republic shit that disney shat out, are they just space marauders or are they Sith aligned fanatics?
Space Pirates, but they're not as cool as the ones from Metroid.
Kind of? A BattleMech is still vulnerable to getting ganked by tanks or some guy with an ATGM or, god help the MechWarrior, an inferno launcher. It's the weird culture of the setting that has mechs matter as much as they do (and also that you the player/reader are here for mechs, not tanks). It's also that it's stated that mechs are pound for pound the most efficient weapons platform available, and the intimidation factor is part of that. Planets also tend to not be garrisoned very strongly in general, and that's why a single Union full of mechs can take them.
That's basically the Tarkin doctrine in a nutshell. They didn't have enough men or ships to garrison every planet in the galaxy, so they make their weapon systems big and scary so that the common normie who doesn't have a head for tactics or strategy gets spooked enough to keep his head down and pay his taxes on time.
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