Look at each game on the Steam storefront and check the Steam Deck compatibility on the right, it’s generally a good guide. COD and FC24 are listed as “unsupported.” Lies of P is “playable” with its ownly caveat being that the in-game text may be hard to read at times, but it says the default graphics perform well on the Deck.
You can also browse Steam by “Great on Deck:” https://store.steampowered.com/greatondeck/
Not to sound rude but do some Googling, you could answer these questions in 5 minutes without waiting for Reddit replies - perhaps that’s one of the biggest strengths for the Deck, the fact it’s so tried and true that you can answer any question you have about it within 1 or 2 Google searches.
Not as comfortable as a first party pad, but the most comfortable handheld gaming device of all time imo. As much as I love my Switch/Vita/DS/etc, they are agonizing for my big hands, they’re too thin so I feel like I’m pinching a hairpin the whole time. The Deck is curved like an XB360 pad so it rests into your palm really well.
And even though it’s heavy, it feels lighter than what you see on paper. The weight is very well balanced. Ergonomics are one of its strongest characteristics.