How competitive does a score of 800 in SAT physics, chemistry, and maths-2 each makes me?

Scores - SAT Maths-2, Phy, Chem: 800 in each.

I would like to know what is SAT 1 equivalent score of such SAT-II scores.

There is no “SAT equivalent”. 800 is just the highest you can get.

The SAT IIs are different from the SAT I. SAT I tests basic college preparation. SAT IIs are like AP Exams in that they test specific subjects.

SAT-II 800 is more common than SAT-I 800.

SAT-1 Percentile Ranks
800 Math 99%

SAT-II Percentile Ranks
800 Math Level 91%