To me the most serious drawback is not being able to add Beneficiaries or POD!! Sofi Bank needs to address this on priority or they will be driving potential customers away.
Joint Accounts, per their website, are insured for 500K. Here is the weblink and extract from their website:-
Are my deposits insured?
Yes, your deposits are FDIC insured up to $250,000 per member (joint accounts are insured up to $500,000). For more information on FDIC insurance coverage, please visit www.FDIC.gov.