Just curious to know Is it bad user experience if user is auto logged in even if they sign up? and not login? or successful sign up should navigate user to login and then after entering credentials sign in??

I personally prefer getting signed in along with signing up.

If it's not passwordless the only reason I can imagine is to just users retype it once more - just to increase the chance of them remembering it the next time. I have been typing in random passwords on most platforms that need passwords for more than a year now due to data breaches. So if I forget, I get a mail to reset now. I think it's much better to use a passwordless solution and/or offer SSO with Google and others. I liked sawolabs.com.

Actually I am working on micro saas app. So don’t want to invest much time in authentication stuff