Those skinny strong guys are generally just lean and not flaunting it by wearing tank tops aka men's yoga pants. They'd look bigger without clothes. To answer your question, eat at your caloric maintenance and lift within the 1-4 rep range. That'll max out your neural pathways and make you stronger while keeping hypertrophy minimal. Try not to get hurt since there's a high injury risk with this strategy. Keep in mind there's a limit to how strong you can be at a certain body weight, so if you plateau for over 4 weeks before you're happy with your strength, you'll need start gaining weight.