What it's going be like right after release?

I haven't played in ages, but I was there when it started, and I don't remember any kicking sprees or screams of fury. I play on PC, which is generally a silent affair, and it wasn't different in the early days of ME3MP if I remember correctly. After all, everyone was a beginner back then!

I wouldn't worry. If in doubt, find three friends to play with and avoid pugs altogether, though I don't think that will be necessary.

My advice would be, if you're concerned about the difficulty at all, to play the singleplayer first to familiarize yourself with the various enemy factions and flow of the gameplay. The difficulty you pick doesn't really matter so long as you are able to get comfortable with what the different enemies are capable of, and how to put the pieces together in terms of gameplay.

The difficulty of the multiplayer will also depend on the caliber of the people you play with. Random pick-up groups will likely struggle on Silver/Gold for weeks or even months, while even a casual group of friends who are communicating won't have too much trouble after the first week or so.

Another thing to keep in mind is that people who work in the gaming industry tend to be worse at games than people who don't, simply because they spend so much time working on their games that they don't have a whole lot of time to play them. Similar story for gaming journalists. But as with any group, there are outliers.

I was not there for launch but I suspect a lot of the console players were salty because MP was perceived as an upsell for the XBL/PSN networks and you had to fork over MOAR MONEY to raise your SP EMS and get the better ending. Biovar eventually made it possible to get the best endings without MP, but for console players already enraged over the ending debacle, the damage was done. So I'm guessing those early console players were not happy campers.

PC players, naturally, weren't as concerned.

IMO, the idea is to get familiar with controls first by playing single player. Then, find some friends to start the MP journey. Then, thanks to their help, get some manifest and become comfortable on 2-3 lower difficulty levels. Then, you can pug. Of course, it is possible to pug from day 1 but it might be a bit on the tedious and uncomfortable side of the things. That was my personal experience with ME3 and DAIMP.

One curious difference regarding ME3MP and DAMP were the Weekend Challenges. Both had Weekend Challenges that were pretty much the same thing.
However, ME3MP got its Weekend Challenges from the very first weekend, thus more people were interested in MP from the beginning. DAMP was released on November 18th 2014, but its first Weekend Challenge took place on the last weekend before Christmas that year.
I pre-ordered DA:I with the intention of playing Multiplayer from the beginning, but when I felt there was very little encouragement for that, I ended up playing Single player only for a month - enough time to beat the game twice. I decided to venture into Multiplayer for real from December 21st, when the first Weekend Challenge came up and I saw that many other players on my Friends List were doing the same.

I believe this time around Bioware's commitment towards the Multiplayer is greater and we might have Weekend Challenges from the very beginning. I plan to start playing Multiplayer from the beginning, but it all comes down to the encouragement for doing that as well as the quantity of time for gaming I have available per day - if I had unlimited time, I would play both from the very beginning.

Correct.

I'm expecting the early days to be chaotic with poor skills and lots of fails.
Should be fun...

As for atmosphere, most people will be fine.
There will be the occasional idiot but such is life, drop out and find another game.
ME3 was much the same.

I'll be hitting multiplayer as soon as possible.
being a noob is so much easier in a pack. 

That said, even if some of the rules have changed, an experienced ME3 player will be going in with an advantage.

Don't worry I'll carry you to victory.

That's great, thank you!

I tend to never play multiplayer first since I like to get a feel of the controls in the single player versus multiplayer. But if I get into one of the multiplayer betas, or both like I did last time, I'm probably going to start on multiplayer to get a leg up on everything. I'm sure there's going to be plenty of people ready to do the same.

I'm going to jump right in and play MP as soon as I can.

I know I'm going to Scrub but I don't care. That will be the time to learn all that I can to carry forward and get better. It will be interesting, it may be a little aggravating at times to get everything down at first such as controls, what to spec out on a character, which weapons to use....etc. Then there are the maps to figure out as well....should be fun to explore those. Everything at first will be learning.

But everyone will be in the same boat at first until everything gets figured out.

I'm eager to see if they will have public access to balance changes and ban waves like ME3,and also where they will post them.