Here's a rundown on what I know of how brushless moors are rated; I hope it helps.
Like the first motor you originally asked about, a lot are rated by the dimensions of the motor cans in metric, and in this case its the 2858 which means its 28mm in diameter and 58mm long. It should be called a 380xxl not a 540xxl as Hobbypartz calls it.
It looks like you already know about the 540 and 550 size ratings, but their respective sizes as above are 3650 (36mm diameter and 50mm long) and 3660 (36mm dia. and 60mm long) and a 380 would be 28mm diameter and 45mm long, so this 2858 motor would be a longer 380.
There are bigger motors, like 3665, 3674, 4068, 4082, 5692 and so on, but they're definitely too big for your application.
Then there is the way Neu/Castle rate motors, which is by motor can diameter and rotor length in tenths of an inch. So a Neu 1415 is 1.4" in daimeter (actually 1.43" or just over 36mm) and the rotor is 1.5" long (I don't know if that's rounded off too, but that's 38mm) and the can itself is 2.75" long (or 70mm) so that would equal a 550L or a 3670 motor in size.
There are other ratings on the motor, but these are pretty much standard across all manufacturers. I'm referring to the kv rating, which is the rpm generated per volt. This should be measured at no load and with no advanced timing. This is the 1200kv and 3200kv from the two motors you mentioned. So with the same voltage, the 3200 would be about 2.6 times faster with the same gearing.
Then there is motor turns, which is just like brushed motors where the lower they are the faster the motor but lower the torque. But you will also see Y and D, like 1.5Y and 1.5D where they represent that the motor is wound in either a star (Y) or delta (D) configuration. This usually also means the motor has more that 2 poles, as 2 pole motors often use a Y-equivalent turn if wound in delta.
I'm getting long winded here, but there's a lot to it. There's also sensor vs sensorless too, but you've got an SV2 so there's no need to get into that.
If you're still interested in a Tacon motor and the 550 Titan has lots of room to spare, I'd recommend a lower kv motor than what you listed the second time to get more torque, like this
Tacon 3660-540L-20T Brushless Motor 1200KV for 1/10 Car Trucks
If you're tight for room, then this one
Tacon 3650-540-32T Brushless Motor 1100KV for 1/10 Car Trucks
The bigger 3660 will give you more torque.
