The initial Soviet invasion of Latvia was led by the Red Latvian army. It was a full division and well motivated, trained and, for the time, equipped. Once there the Soviets tried to recruit another division, but it was never much good.
What the Soviets found, though, was that the Latvians had a tendency to desert –their love of Soviet power not over-riding their desire to go home after so many years away. The huge abuses of Soviet power in Latvia didn't help either. Lenin pulled them out, reorganised them and sent them south, rather than see one of his better units evaporate completely.
So while the Latvian division did fight the Freikorps, both the initial invasion and the later retreat, I'm not sure I would describe it as "heavily engaged". It was all pretty small scale – a large battle was a battalion – and both times it was more a swift rout than anything else. (The heavy Freikorps fighting was with Estonians and Latvians.)
The Soviets never fully conquered Estonia, and the fighting there was much more prolonged and intense. The Soviet Red Estonians were recruited later and showed every bit the inclination to desert that the Latvians did. So they also got pulled out and sent south to fight Denikin at Orel (rather than face Iudenich on the Estonian Front).
The Red Polish Army was more a PR exercise than anything else. Poles and Russians don't mix well.
The situation in Ukraine is beyond complicated – just counting the different factions takes a while. You have the Red Ukrainian Army, defecting Red Ukrainians under Grigoriev and on-and-off Red Army of Makhno, two Nationalist Ukrainian factions (three if you count Skoropadsky), numerous Greens, Ukrainian Poles in L'viv, Poles, Whites, French and Rumanians.
Note that no stage were any of these separate Red armies. They were ethnically raised units, sure, but under direct control of Moscow at every stage of their development. They had no say on where they went, nor were they consulted on any political matter. Lenin didn't do independent centres of power.