ispeed or igrow?

I want to start a NISA account and I already have Rakuten bank so I imagine it’s best to go thru with Rakuten securities. I’m a little confused because there’s ispeed and igrow and I’m not sure what’s the difference between the two and which is recommended for what purpose. I’m very much a beginner to investing but I want to learn and invest more outside of NISA too eventually… but baby steps first. What should I use to start NISA?

by pipluplu