MPEG4 X264 vs NVENC H264 encoding play compatibility on old devices

Question

I always encoding videos on x264 , this encoding work well on old devices or mobile phones.
To increase the encoding speed I try to replace encoding method with NVENC H264 with nVidia GPU.

Question 1 : Device combability for play the NVENC H264 is different with x264 ?
Question 2 : Old devices can play NVENC H264 file same as x264 ?

Old devices : (All devices that can play x264) Android 6+, TV Setup box, TV, Google chrome 48+

Answer 1

H264 is a decoder specification, not an encoder specification. To be an h264 encoder, it must produce a stream that is decodable by all h264 decoders.

So, yes the files will still work.

Note however that h264 has profiles and levels. So if a devise doesn't play a file, it's because the level or profile is too high.