Cold Email vs. Cold Call vs. Linkedin -- Networking Strategies in 2020

Curious as to what strategy those on here have found the most effective for getting in touch with people in a given firm. Obviously the best / easiest is to be referred / connected by a mutual contact, but that's not always possible. So in cases where you don't have any connections and no alumni to leverage, what have you found to be the most effective? Sharing my personal experience and views but quite curious to hear what others have to say

• Cold Call -- I used to cold call during my undergrad days, but now being on the other side of things, I think it is a pretty bad way to get in touch with someone you don't know. It puts them on the spot and in an uncomfortable situation and I don't think it helps your own case. You can ask to get in touch with HR, but that's only marginally more helpful than dropping your resume in the general mailbox

• Cold Email -- without any connection to the person, this seems to be the most formal / appropriate way to get in touch. While it does involve figuring out the email format, this is not that challenging. For anyone at a fairly senior level, I think this is the best bet, though without any true connection, the response rate is relatively low.

• Linkedin -- obviously a much more casual and informal way of connecting with people, but seems appropriate for connecting with people who are a bit younger, removing some of the formality from things and allowing them to easily see your background quickly. At this point I usually have at least some mutual connection with most bankers / investment professionals, which may give comfort to someone I'm reaching out to. That being said, it involves adding someone on Linkedin and then messaging them after they accept the request, so two layers to ultimately get a response.

What are your all thoughts on the above / what has been your experience?