Note that there is nothing stopping you using a GW (samsung) on a pixel - sure certain health metrics require samsung app/phone (but possible to sideload) but no hardware reason they can’t work.
Its worth noting that if he does get an iPhone then going forward there will be limitations in terms of being able to reply to messages as Apple locks this down to apple watch only.
NFC excluding apple and wear os (android’s mobile operating system) is pretty limited:
Fitbit might be an option as works with android and iPhone and uses google wallet - but they don’t sell in all countries anymore and limited to quick replies on android and no option for replies on iPhone; and personally I think the fitness features are woeful.
Garmin: Gamrin pay is on most garmin’s but they generally aren’t overly supported by a lot of banks in most countries, so you would need to check in your region as to which banks or digital services support it. For example in my country you are limited to 6 banks and 3 digital services - so its was very easy for me to set up a digital service which is direct pass through to my normal credit card so still get my points etc (just like I was using my normal card) - had it set up, agreed and loaded on the watch within 30 mins. The best option for you would be the Venu 3 (or venu 2 plus at a pinch - no full replies on android, but can do it via leveraging phone’s voice assistant) as it can do full replies to texts on android, and or you can leverage the phones voice assistant on android or iPhone to make those replies if wanted. Its a 45mm case with a 1.4inch screen (or can go for the smaller 3s); and being a garmin it has excellent health features, excellent fitness features (compared to smartphones, but only very good when compared to fitness watches), and includes some basic training metrics and analytics like VO2max, Recovery time and workout benefit. Biggest issue is going to be price - not sure you will find it in the range you are prepared to spend! There are cheaper options like the Vivoactive 5 that has nfc an in your range, but like the rest you are limted to quick replies on android and no repiles on iPhone.
Amazfit Balance has NFC but only applicable to Curve - and not sure thats an option for you. Reply is quick on android nothing on iPhone. fitnes features are Ok, and it while it has good training metrics they don’t overly work well as the HR is only good and they are still learning how to apply training metrics so they can be reallly hit and miss. Fitness features are on the good side for a smartwatch but can’t match the fitness brands or what apple can offer if using 3rd party apps.
Huawei watches do offer NFC, but like balance its really restrictive - so you would have to check if even an option in your country. Relpy like the balance is quick on android nothing on iPhone. HR is very good, gps is meh on most of their watches, but the Good HR doesn’t always equate to good health metrics - really hit an miss; some models offer training metrics but again like amazfit - they are based off what garmin does but they don’t have them right yet, so really hit and miss in terms of good training estimations. Fitness features are on the good side for a smartwatch but can’t match the fitness brands or what apple can offer if using 3rd party apps.
Wear os watches - not included here as most are locked to android. Not sure if any are currently able to work with iphone (i know the fossil gen 6 did). However like the rest, while can do full replies on android, locked from doing that on iPhone (if it can connect). Of course has google wallet which is massive bonus. Fitness features in most is pretty woeful comapred to a fitness watch but some of them do have the odd interesting feature i.e. GW watchs including running dynamics (though very basic); the new oneplus watch 2 includes a lot of ball strike metrics for racket sports and might be tempting if racket sports are main focus.
Note: depending on fitness features required - that might swing/determine best option.
Note: NFC isn’t essential if you are generally going to have you watch on it. Might also be worth considering that it may be possibe to get a NFC watch strap or ring - as may be an alt option. Note that most of the watch straps tend to be on the quick release watch strap system so may not be an option for a proprietary watch system like what apple watch or pixel watch 2 uses. I know that garmin (at least for the venu 3) and huawei use this as their main strap system.
