I dont want to think about what that would sound like infront of a 5150.
Presumably it might not sound utterly dreadful if you were running the 5150 much cleaner than usual? Although I guess that kind of defeats the point of having a 5150.
Yes and yes.
Theres nothing to stop anyone from trying, and theres nothing that I know to say that it hasnt been done on some well known record or other, but the question being about how what pedals are generally used in death metal sounds, the answer is overwhelmingly HM2s into clean or near clean SS or 800/900/similar and TS-type (set with max/high level and low/min distortion) as a boost into something high gain (lions share 5150s and rectos). Though I'm not sure the distinctions are really worth anything, or are meaningful at all as descriptions, the former is the classic 'brutal' sound and the latter is the more modern 'tech' sound, along with a huge swathe of non-death metal.
That being said, that the TS -> 5150/recto -> V30 -> 57 -> API sound is absolutely all over modern metal, you could say that the only real answer for 'death metal sound' as opposed to 'sound used in death metal' is the HM2.
That doesnt mean to say that the same tonal ballpark cant be achieved in many other ways, but they are by far and away the most common scenarios.
Edit: also quite a bit of DM (more than elsewhere afaik) uses SS amps without a pedal. Some crates whos name espapes me, marshall valvestates, and especially the ampeg VH140s have all seen quite abit of record time.
