Whats the difference between contacting via contact form and via email?

I need to contact about 100 agencies/ freelancers regarding freelance work / partnering / working with me. They are very narrowed down niche agencies.
I scraped their email from their website. I got email of 50+ agencies from their website and rest of them i didn't get. So for 50+ of them I will have to fill the contact form and contact them.
Not trying to spam because its only about 100 agencies that I am trying to contact. But its still cold emailing as they don't know me.
1) So whats the difference between contacting via contact form and via email, in this case contacting an agency?
2) Which will get better response contacting via email or via contact form?
3) I am gonna use my gmail , icloud, outlook and or yahoo mail. Because its like only 100 email I gotta send. Do you see any issue with that?
4) Should I use my company domain email? If so do I need to warm it up first?
5) I used this free tool to scrap the emails , https://www.softtechlab.com/web-email-finder . Is there any better tool to scrap email from websites? as I got email scrapped from like 50% of the website using it.

Probably I am thinking it too much as its not many only like 100 emails. But I need to hit the inbox as there are only about 100 agency in this niche. Is there's any better approach to this?

Do both if you could. 2 is better than 1.

Looks like I can get emails for most of those website by visiting it and / or with hunter.io chrome extension. One advantage I see with emailing them instead of filling contact from is that I can craft an email sequence and send them increasing in my chances of engaging with them.

IM Rider said:

Looks like I can get emails for most of those website by visiting it and / or with hunter.io chrome extension. One advantage I see with emailing them instead of filling contact from is that I can craft an email sequence and send them increasing in my chances of engaging with them.

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You probably have done your emailing by now but yes, I think that you will have more success with a direct email.
I am building a cold email campaign and would love to talk with you about what was your strategy, pm me if you have some time

No I haven't, I got busy with other stuff. We can talk here.