Are these SV based? SAFEs have wider acceptability here than elsewhere. It's pretty uphill to get people to use a legal instrument when they're not familiar with it.
For the SAFE terms, you can tell them the gold standards in San Francisco.
For the VC group invested in competitor - if a direct competitor, would assume that they would share info with the direct competitor on things you tell them, especially if they are lead investor in the competitor or have a board seat/observer role. If they are indirect competitor, it may just be that the investor has a focused theme in your space, and legitimately doesn't think you compete with the portfolio company the same way you see it.
Typically, non-leads are less involved in information sharing, though it could still happen depending on their style. You can ask directly if they see a conflict between investing in the two companies and gauge their response.
SAFEs are not as widely accepted outside of Bay Area, angels prefer convertible notes instead.