Help Me Understand DACs?

Hello! Fellow pea brained noob here again.
I understand that every piece of modern technology from your stereo to your sister's vibrator has it's own (probably) shitty quality DAC of its own.
I also understand the way an input signal gets diminished by my precious Bluetooth & impacts SQ.
I've heard many claim that a high quality external standalone DAC may aide if not fix the problem entirely for the best sound quality.

Here's the fun part:

I know they're wired directly to your stereo input & amplifier respectably. I'm regrettably & unbearably slow when it comes to assuming its' functionality throughout though.

Is this equipment that I could mount up and hide inside my dash to easily forget about?
In a perfect world I'd like to keep on wireless streaming my jams directly to the HU.
Am I missing the point anywhere? Would an investment like this be an automatic miracle supplement or rather a pain in my back side worse than sciatica? Are they worth the extra dough?
I sure hope I wouldn't have to connect my phone directly to the DAC because that might be a deal breaker for me.

Please offer any knowledge you have on the subject. It's much appreciated thank you!

If you have a dsp you want an spdif bridge not a dac… go digital in… but any decent connection will be wired. That includes dacs and spdif bridges

Bluetooth can’t even send actual cd quality never mind any kind of hi res signals without compression via a codec that’s lossy

wifi devices are few and far between… there is the little $120 Wiim mini, but unsure if you have to mess about connecting every time ����

Ohhh word thank you! I thought the job of a DAC was to decompress the signal where Bluetooth and similar fucked shit up.