If you're going to have a hard pull show up on your report, you might as well apply for the top cashback cards. 3-4 cards typically puts you in 10k+ total credit territory and plenty to remain under 20% utilization with mustachian spending levels.
We do semi-regular credit limit increases (hey, why not have lots of available credit - it's like increasing the E-fund!). But we
never have them do a hard pull. They (Citi particularly) will give you an increase in your limit of ~10% every 6 or so months with no hard pull. Strictly based on income.
Our credit limit is near $80,000 (didn't realize it was this high until just now! Not sure when/if we will stop, ha!) and we are not quite 30 years old yet. We have 1-2 "regular use" cards, and a handful of cards we use very rarely.
Our utilization is well under 5% monthly, and always paid off monthly. However, we are currently taking advantage of Chase Sapphire 0%/0fee balance transfer offer on ~$10,000 (already invested), so having a larger "available credit limit" helps our credit score not take such a huge hit.