Seeking opinions on boiler options and sizing

Hi all.

First, thanks for this forum. I've learned a lot by doing some homework here.

I have bids to replace our ancient oil-fired boiler and tankless coil (natural gas is not available here.)

1100 square foot house on Cape Cod, with one bath, four people at most, and recently completed air sealing and insulation through the Mass Save/Cape Light Compact program.

I did my own heat loss calculation using the slant fin calculator and came up with 28,600.

Contractor #1 sized the boiler using the radiators, and is suggesting:

1: Burnham MPO-IQ 115 with IQ

2: Buderus 115 WS/4 w logamatic

Contractor #2 did a heat loss calculation, and come up with 30,000 and suggests:

Slant Fin Ec-13; no outdoor reset

Contractor #3 sized using the radiators, and is suggesting:

Buderus 115 WS/4 @ with logamatic (as did contractor #1, at a different price)

All have offered indirect dhw options, which ill get to after I figure out the boiler (if that makes sense.). I'm planning on a 40 or 45 gallon.

Question 1: aren't all of these options these oversized?

Question 2: would these boilers require a chimney liner? (Contractor #2 mentioned this. I thought this was an issue with condensing boilers, but not these types/models?)

What do you all think of these options? Any advice, suggestions for additional homework/research, etc?

Thanks!