@jonnylugs Here's the bottom line - you need to be in a caloric surplus to add weight. If you go too high in a caloric surplus right away, you'll add fat faster. Think about it as two elements to an equation - calories and metabolism. Metabolism is your ability to use calories. If you add 200 calories, your metabolism needs time to adapt, to be able to catch up to that increase. For the first 2 weeks in a 200 cal surplus, you might put on a pound or two of fat. But, your body will learn to utilize that energy and in the long term you'll have more energy for your muscles. When you try that for a month and you start getting hungry again, add 200 calories. You need to train metabolism with progressive overload.
Any fatty meat is going to have good cholesterol content, but it's hard to replace red meat in terms of available amino acids. There's also the factor of how lean meat might increase the thermogenic effect and therefor end up burning more calories (40g protein, 160 calories, might net a total 100 calories after that factor, for example).
If you are eating vegetarian, it's going to be hard. You need to really look into amino acid pairing for every meal so that you are getting a complete amino acid profile. There are also essential amino acids (the ones your body can't make) that aren't as bioavailable in vegetables.