Hi all!

I'm new to Odoo, but I'm developing a website for a client, and they want to sell a product. They are using Odoo Online, and they set up the product, payments, leads and everything in Odoo, and various types of leads have different pricelists (end customers, dealers, etc) so all the standard stuff.  

However, due to the specifics of the product, the need for things like a 3d configurator and various other custom functions, we are developing a nextJS product website separately from Odoo. 

What I would like to do is one of the following options:

a) (ideally) have a log in button on my page which would let customers log in via Odoo, at which point I could get from Odoo the type of customer they are, and request product information specific to that customer type. Once they have configured their order, we take them to the odoo store cart, which we pre-fill, and they complete the purchase there (and they are already logged in).

b) not have a log in button but still take the users to the odoo cart without login, but pre-fill the cart and then ask them to log in or create an account, at which point the final prices show up and they can complete their order. 

Is any of this possible with Odoo online? I understand a custom module would probably easily solve all of the above, but I don't think anything except Online is an option, so I'm just trying to find a viable solution. 

I'd appreciate any pointers, and if I haven't explained something properly, please let me know, I'll gladly provide further details.