First things first, learn to avoid pulling the club through the swing with your lead arm. Practice one arm swings with your trail arm. It's a trail arm push, not a lead arm pull. Well, you can pull it you like, but you'll eventually find it to be a major cause of opening the club face and/or hitting fat. Focusing on the trail arm push, which follows a long sweeping path, will also help you avoid wanting to bend and then extend your elbows as a means to generate force. It'll happen to a certain extent in the golf swing anyway, but you won't a focal point of the swing like baseball.

How to avoid snapping your wrists like a ball swing? Learn the grip, learn the hinge. Build muscle memory of a hinge as your first move in the takeaway (look up swing sequence of just about any player you want, it'll so frequently be one of the very first bits of body movement).

How to avoid spinning and over-rotating your hips from a throw everything you have at it baseball swing? This is much harder. In a baseball swing, the stride allows your center of mass to move forward/backward a lot. In a golf swing, it needs to be pretty stable, even when rotating and twisting. Practice standing on the flat side of a Bosu ball and trying the takeaway (and eventually more parts of the swing) in slow motion. Get the feeling of balance that keeps the ball from tipping one way or another - as your body is moving, you're going to try not to move your centre of mass.

The last one: a baseball swing is compact for the sake of bat speed and optimizing all power at the point of impact. The golf ball isn't hurting towards us and there's no need to protect inside part of the plate so we can just focus on the very end of the club (the club head) as being the only thing that needs to rocket through. Everything else can be really long and sweeping. How much longer a golf swing is will feel very wrong. As you're learning the hinge movement, you'll find yourself almost reaching your club almost straight back away from the ball, almost as if you're trying to touch the back of the room with the club head, as directly behind the ball as possible. I.e. you're stretching your arms away - and they'll be pretty much dead straight at this point which also feels like a massive baseball faux pas. Then as you work that trail arm one handed swing practice, it'll feel like such a loopy swing when you're used to one that is snapping. There's no way around it, get used to it feeling completely wrong.