Patricia below gave good solid advice.
If he is fine in the crib... then let him sleep there. Or, segue him to a mattress on the floor. That is less intimidating than a bed, bed.
And with that, there are different expectations, once a child goes to a "big kid" bed... so be very careful and thoughtful of that. When there are TOO many "expectations" upon a child... when they are not ready, it will be hell for them and very difficult.
From what I know, when there is a new baby coming... the "expectations" a parent has UPON the eldest child... changes. The expectations becoming more and not necessarily age appropriate nor in line with the child's readiness nor ability. THUS... this puts a great deal of STRESS upon the existing child. Not always fairly. Remember, a young child has very little shoulders... they simply cannot carry all that stress/burden upon their shoulders. Thus, not coping well.
"Expectations" of a parent, upon the existing child... has to change according to the child's maturity and ability... not just because there is a new baby coming into the home. If too many expectations, and suddenly, just because of a new baby... it will not be easy, for the eldest child. Thus they act out.
I would, just kick back with the potty training.
"Regression" in a child, signals stress in a child or inability to cope. Do not punish/scold for this... they are only coping in a way that a baby/child knows... they do not have the sophistication to reason it out, in light of their emotions.
ALSO, "emotions" at this age is NOT fully developed yet. Thus they act out and cannot categorize their feelings nor sort it out or understand the full abstractness of it. Yet. Your baby is ONLY 20 months old. He is dealing with a lot right now... and with his Mommy changing... for baby. Not him. In a child's mind... this is how they feel. And your body and appearances are changed too... and what not. A child feels all of this.
Help him to communicate BEFORE baby comes... teach him the words for feelings... and that it is "okay" to feel sad or grumpy... but you are both a TEAM... and you will always help him, not just put "expectations" ON him. That is a lot of pressure. AND, at his age, on the cusp of 2 years old... they undergo a TON of changes physically and cognitively... and it is NOT easy for them... plus HE has the additional issue of a baby coming. HE is having a baby too. Not easy. So try to give him sympathy.. understanding.
When I was pregnant with my 2nd child... I spent a TON of time, on my first child, prepping HER for the baby. I spent lots of time talking with her about it, taking photos with her and my growing tummy every month, I let her talk to my tummy and hug it, we shopped together for "big sister" things and for her baby brother, I took her to all my prenatal appointments which the Doctor encouraged and he even taught her how to place the heart doppler device on my tummy to hear the heartbeat. I basically spent lots of time prepping her... so she felt "at home" with the process of me being pregnant and HER being INCLUDED in it... and a part of me. I also told her that after baby is born... that he will cry and need to nurse. But its okay... that is Mommy's "job." She can help me love him. But that SHE is my 1st baby.... and always will be, and I love her for that. She is special to me.
So, with all of the prepping I did with my daughter while pregnant... it really helped in the process of during the pregnancy and after baby came home. She adjusted better. I really just everyday, spent time with her.. and my growing tummy... and it made her feel secure.
If you can... let him sleep the way he is secure with. Giving the crib to baby, "his" crib... can be unnerving for a child. They can feel pushed aside. AND... that their things are not theirs. I even would explain, before I had my 2nd child... that my daughter's things were HERS... that I understood that... and did not expect her to give or share everything... a toddler needs to know this. Their things are like their territory... and even simple things like that can upset them. So, my daughter would choose which things of hers, she'd share and which one's were too "special" to share. It gave her control over it... over her life. A compromise... instead of everything being just for baby.
Anyway, sorry for rambling, but just some things I did.
All the best,
Susan