Experiences to share with building a digital S&M platform?

I am in the early stages of building up an internal proposal for a sales platform based on various tools, to help drive and nurture our leads. Our company sells B2B SaaS, and are transition from having a poor webpage and an outdated CRM system to something that can automate and improve the early stages of a sale. I was hoping that someone with experiences from a similar implementation would be willing to share some thoughts and experiences. Pitfalls, successes etc.

Midways to where I am today, I got convinced that Hubspot was the obvious choice, but their license model is killing us. We're a small company, but since we have two domains we had to go for the enterprise package unless we wanted two separate databases. We could not justify that, so have currently abandoned that option.

My current plan it so use
Squarespace to host the webpage and blog.
Mailchimp for landing pages for PPC campaigns, and various lightboxes. Also newsletter, but that is secondary.
Mailchimp to manage the trial information emails, giving us insight into what works and don't work.
Pipedrive to manage the deals, and sync with MailChimp (via PipeChimp) to have user actions visible as notes in the deal record.
Zapier for various integrations and automations. For instance email alerts on activities in certain pipeline stages.

Also Google and LinkedIn for PPC campaigns.

Other tools I have been looking at some if ActiveCampaign and Instapage, but conceptually I want to keep the total list short. Thus Mailchimp.

Anyone been through a similar journey? Was it manageable?
Any specific experience with the integration of these tools, is it stable?

Any input is highly valued!
Tom