@fatherted i know that Samsung TVs are reliable and get a good write up but if the budget is there, honestly go for the OLED – LGs are the cheapest, and for retro gaming the cheapest is (in most cases) what you are wanting to go for because we as retro gamers are only buying this for the panel and not the fancy processing it can do. The benefits to some other OLED tvs are mainly better speakers, such as in the sony OLED range (AG8 & AG9 for uk, A8G & A9G for US) where there is essentially a soundbar set up behind the screen and the sound comes through the glass which is a cool effect and a good space saver since you wont likely want a soundbar unless you are an audiophile. The only other good feature you will find in the expensive OLEDs (Panasonic gz2000 & sony AG9) where the company has done some tweaking to the panels to increase contrast, brightness and heat distribution – i wouldn’t worry too much about this, stick with the cheapest ones for this.
As far as lag is concerned, any OLED in game mode will have an inherently good/low lag because of the nature of the screen technology itself, to be sure though the best way is to head over to the website displayspecifications and they will give you the value for the input lag on there, along with loads of other information about the TV and its specific specs.
TL;DR cheap OLED is the way to go, lag is inherently low on OLEDs so choose whichever you can find at a good price and im sure you will be happy.
(i should really do a full write up on tvs for ossc/retro use on this forum to help out those who are not as familiar, if anyone wants that let me know)