So I looked around the web and couldn't find anything regarding card and bank validation methods that Stripe had in v2 but in v3:
Stripe.card.validateCardNumber()
Stripe.card.validateExpiry()
Stripe.card.validateCVC()
Stripe.bankAccount.validateRoutingNumber()
Stripe.bankAccount.validateAccountNumber()
and so on ...
Are there any equivalent methods in Stripe v3 to those above which are from v2?
stripe.js v3 doesn't have those methods. Instead you will create an empty div and mount it, let stripe.js (v3) handle all that validation for you.
For reference, here is the standard integration in their doc