This topic goes around and around.
We do not know the solution but it can be any or all of the above.....and a few more.
My advice is start with the cheapest and work up to the dearest.
Bear in mind you may have caused enough bruising that a week or so out of the saddle may be a good idea and thats free.
Dont wear undies with cycling shorts. Cycling shorts are made without sticking up seams, undies are not. I often wear two pairs of cycling shorts for double padding. It works for me.
PLENTY of cream, all over the area, not just the effected area.
Play around with the seat height, pitch, forward and back. Very small adjustments can make a big difference. Take your seat tools on the ride and adjust as you go along. When you have got it right, take careful measurements and write it down. Mine are on my workshop wall. I cannot lose my workshop wall. I use a ruller and a spirit level to measure the seat.
The last thing is replacing the seat. Its and usually the cheapest, most useless thing on a new bike because the manufacturer know that many people change them for their favourite saddle.
Not everybody has a Brooks arse. I have 3 Brooks saddles and they are great. The B17 took 2 years to break in and is great, but it almost got binned many times. I have now changed over to Charge Spoon which I love. They are cheap, colourful, not leather, dont squeak and everyone is great out of the box .....for me. I would rather take a gamble on a £20 Spoon than. Brooks saddle which are very expensive.
I can ride a century without too much discomfort and do it again the following day, so I must be doing something right.
These are only my opinions, but I hope they help.