Is reaching out to a friendly investor or advisor different from board outreach?

Yes when you have an existing relationship. Asking a friendly investor for a warm introduction is a normal sales motion. Cold outreach without prior relationship is the high-risk path.

Should I email the board member or message on LinkedIn?

LinkedIn is slightly safer because it is publicly understood as a peer channel. Email reads as more presumptuous when there is no prior relationship.

Are there situations where bypassing the CEO is appropriate?

Almost never. The very rare exception is when the CEO has explicitly blocked legitimate engagement and the issue is genuinely material to fiduciary duty.

How does this differ for VC-backed vs PE-backed companies?

VC-backed boards tend to be more accessible because investor partners actively look for portfolio support. PE-backed boards are tighter; partners protect their portfolio CEOs more strictly.