Hi Brian
Get a 27′ Apple Thunderbolt Display, a used one. They are around 300.- to 700.- CHF (in Switzerland), often in very good condition. Take look at tutti.ch or anibis.ch or ricardo.ch
You can tap in the level of brightness like on your macbook.
The quality of the build is unreached
The display has beautiful colors and is very bgriht, (I often use it around 70% brightness)
the resolution 2560×1440 is great
thunderbolt 2 connection fits directly in your macbook 2015
you can provide your macbook with power with the magsafe cable coming from the display
I found one for 220.- CHF and I couldn’t be happier with any other monitor sitting next to my 27′ imac 2017
best regards from Zürich
Lutz