There is a difference between monoblock and split. With the monoblock, noise is only made outside, while with the split, the compressor hums inside and this can be transmitted to the walls depending on the installation.
You can install or replace a monoblock yourself without a refrigeration technician.
Split units require smaller core drillings and you can lay somewhat longer distances to the heating room, although shorter is always better.
We have a 9kw Panasonic monoblock j with evenes sps600 and fristar3wp inside, which is actually a tuned 7kw heat pump, both devices start with 500-600 watts power consumption and thereby produce up to 2.4kw heat. I did a lot of the installation myself and accordingly, the 9,000€ was mostly material costs.
The outdoor unit stands on rubber buffers on a concrete foundation and is connected via flexible hoses. This makes it largely quiet. Between the technical room and the living area, the interior wall is made of 24cm calcium silicate brick, so you get zero noise.