Except for the usual close border tension or if they were somehow allied with them, no they won't react.

Minor civs can use colony ships and troop transports, but they don't construct them. Not 100% on the troop transport thing. They probably got a colony ship from an ideological trait or an anomaly.

Won't DOWing Minors also help to increase war monger negatives towards you? That being said, if you need those planets and it fits your game plan go take them but be prepared for a pissed off Thalan as now you'll be sharing borders as well.

Wait what, 5% chance to take over the planet of Tortoon and I did it on first try

I snagged both Tortoon and Arken but lost the Erwin to talaan culture. So I'm pumping up the culture on both planets in attempt to get Erwin back because I did the fighting for it. Tortoon was considerably easier because it had base 10 influence but Arken is harder one. I held onto Erwin for like five turns.. and lost it.

Although nothing beats Thalan waltzing into my territory and colonizing Mars only to lose it to me in one turn. lol That one happened in last game. Made me laugh. That one happened int he game before the one i'm currently playing

Both Tortoon/Arken was still in neutral space so it was no problem. Although Thalan border was slowly approaching both planets.

Morale haven't been a problem after I got a certain tech in trade from Iconium. My overall morale has been at like 96-100. I can't remember what that tech was but it was awesome. Newer planets tend to drop in morale until I get entertainment buildings built.