Hello! I am new to this site after being a long time lurker. After not being able to receive specific answers just by looking at old threads, I decided to make an account, so here I am! I am really wondering about what is the best snake for me. I am a responsible pet owner who will take care of it for the WHOLE it is alive, whether it's 3 years or 30 years. Some things I am looking for in a snake:

Docile

Medium size (5-7 feet)

Not too skinny ( I like a bit of girth)

Not too expensive ($200 and under)

Cage no bigger than 4' x 2' x 2' ( I am looking at modifying a christmas tree tub- seems to be the best and cheapest way to go)

Although I am perfectly aware that snakes can be unpredictable and bite, I would rather it not be something that is know for being aggressive/ defensive (like GTP and ETB)
I myself am fine with being tagged a few times, as I know that is part of owning a snake

The three options I have really looked into are:

Dumerils boa (probolly my #1 choice)

Carpet Python (jungle or iran jaya)

Columbian BCI (male- how big have you seen males get? I have heard contradictory things.)

Thank you all in advance