I want to provide bonus help to people buying my product is it wise to use one of my emails for that ? Also for refunds etc
Every website should have a contact page, abut page, Terms of Service page, DMCA Page, Disclaimer page. Why not add a contact form on your contact page that way it would eliminate the need for your email address. However, I always have an email address on mine. Just set up a special email address for that if you decide to show one.
Are you asking if you need to have a email id instead of say a gmail one? Yes you definitely should. Sending an email from your @websitename.com email address adds an additional level of credibility and makes people more reassuring.
I would certainly have a contact email on your website. You want people to be able to email you have they have a pre-sales question or in the event that there is a problem after they have received a product or service.
Yes you should include a contact me page, to enable your customers to be able to talk with you, and work with you if need be.
It would be helpful to potential clients if they have access to more contact info, especially email. However I would have one setup especially for that, and not use my person email address or else it could get messy and disorganized.
That is a must . A website that do not have contact , your conversion rate will be likely low due to lack of trust. You need a email address with your domain , it show your professional services and gain customer trust. Usually people will look for further inquiry and contact you if your product or service need more process in order to close it .