Can I use Scientific Calculator for CFA Level 1
The proctors won’t allow it.
Just stick to the Texas BA II Plus or HP 12-c
Scientific calculator for a scientific exam, financial calculator (BAII or HP12C) for a financial exam. 
Just learn how to use the parenthesis and flying blind on the calculations. I remember starting for L1 and being concerned because I couldn’t see the formulas being computed, just answers being spit out. You’ll get used to it, and now I actually love my BA II
Also BA II Plus 
No I came from a science background too and a the BAII Plus Professional is the best one for the test.
I passed level I and I’m glad that I paid up for a calculator that can do the corporate finance problems faster (discounted payback period, etc). It will help save valuable time on the exam.