Frankly google sheet will take you a very long way... Attio and most CRM are built for teams with sales pipeline, not a solo founder trying to find PMF.
Most of the features aims at describing complex sales processes and collaboration.
So basically what you want to do is to try different takes (cold emailing, phone, events, influenceurs), get your first 50 customers, try to understand the process (who takes the decision, who will pay, who will use, etc) and based on that, design your CRM to match this process.
My 2 cents (saas solofounder with 6000 users): very important not to overengineer everything. As dev it's our natural tendency but your time and marketing effort is probably the biggest leverage you have.
So basically what you want to do is to try different takes (cold emailing, phone, events, influenceurs), get your first 50 customers, try to understand the process (who takes the decision, who will pay, who will use, etc) and based on that, design your CRM to match this process.
My 2 cents (saas solofounder with 6000 users): very important not to overengineer everything. As dev it's our natural tendency but your time and marketing effort is probably the biggest leverage you have.
Good luck :-)