Great question! Yes this is totally possible. It's actually the best way to do it, rather than using an "all in one" funnel tool in my opinion. You have so much more opportunity to use best-in-class tools like Unbounce when you build your own funnel.
So it really depends on the client, but one of our most common stacks looks like this:
Unbounce for the landing pages
ActiveCampaign for all email automation and sales/CRM tracking <-- This is our external brain
Zapier for "gluing" everything together <-- It is so useful!
ThiveCart for the shopping cart (we don't do a lot of ecommerce, so this is primarily for projects that require a digital download or a something like that. You can also use something like Shopify, PayPal, Gumroad, or SamCart. There are lots of good options depending on your needs)
Google Analytics and Hotjar for quantitative/qualitative analytics
And we just started playing around with Klipfolio as a dashboard of sorts for more tracking
At the end of the day, all you really need are your Unbounce landing pages, some way of sending data to and from an email automation tool with the proper tags, and a cart. The hard part is coming up with the right lead magnets, tripwires, upsells, email automations, etc.
Let me know if you have any specific questions about what I covered. Good luck with your funnels!