DLA to PIP. ESA to UC?

Hi guys.
I helped my friend to register him on here as he really needs some help. Never seen him so stressed. He is on DLA High care and low mobility and ESA support group. He recently received a letter asking him to apply for PIP which is stressful enough anyway however it comes to mind that regardless of the PIP outcome it will also trigger his ESA claim to be transferred to Universal credit? Is it correct? I guess in that case he needs to be prepared for ESA to be terminated and apply for universal credit? Any help would be much appreciated. He is really really devastated. He takes three different antipsychotics, regularly visits psychiatrist but this news comptetely ruined him.
What really concerns me is that he goes into extremely deep depression with unctrolled, really scary rage attacks to follow. It terrifies everyone, including his family, who don’t feel safe to be around him, which makes providing help he needs really difficult, so I really don’t know how he’s going to pass face to face assessment. One moment he is perfectly healthy, stable, articulate person two minutes later something minor can trigger incredibly frightening rage outbursts with him saying awful things and then he is utterly exhausted, basically almost in vegetative state.
I am concerned that whole process will make things for his mental health much worse,

Hi Gordon.

Thank you so much for your reply.
He now can spend hours staring In one direction, grinding his teeth, and almost not blinking until his eyes become watery. It is a pretty scary look. I can’t see him getting any better anytime soon.
We read quite a lot on the internet regarding migration from ESA to UC. It says that certain change like change in money coming in can trigger migration from ESA to UC. So if he gets less or more on PIP to what he gets now on DLA wouldn’t it trigger natural migration?
I am really sorry for asking it second time as we all need to know it 100% to stop him getting stressed even further. Your help is of a great essence for us all.

Huge huge thank you Gordon.