can HOA president prevent board member from requesting violation notice letter to resident

What's with these cryptic questions - I get the feeling there's a lot more to this than what you're saying and I find the details can turn such answers on its head.

There may not be anything specific that says yea or nay to your questions, but doesn't your community have a written policy on this stuff anyway? Have you read the CCRS to see if it's addressed - you might want to start there. If there's no specific policy, the board can draft one - have you checked to see if there is one?
You don't say if you're on the board - if you are, put something together which could address those issues and a few more, then bring it to the next board meeting and brainstorm suggestions.

If you're a resident and you have a concern with a neighbor, I would start by talking to him or her in a nice way (keep the social distancing rule in mind). If that doesn't work, file a complaint against the person with the board or property manager, so it can be investigated. If they investigate and find there is a violation, a letter could be sent (that's usually how this works). By the way, CCRs can be enforced by one homeowner against another, so if you're really ticked, you could take legal action against the neighbor yourself, so you don't have to wait for the board.

Same question asked in the thread "authorization to send violation letter" from yesterday.