Thank you for your question!
It is okay to use a pen 0.8 to write in lower case letters. Generally speaking, the thinner the nib, the smaller the hand force required when writing, because there is no need to exert excessive force to control the handwriting, which has a better effect on writing. The 0.8 nib can present more details and precision than a thicker (such as 1.0) nib. However, the specific pen tip to use depends on your personal writing habits and feel. It is recommended that you try out different pen tips to find the writing method that suits you. Hope my answer helps you.