@Elvon Bowman Thinking big is important, but it's also helpful to take a practical approach. My replies to your questions are below.
1. Aiming for larger properties on your first deal (100+ units) is definitely very ambitious. It's certainly not impossible, but it's probably going to take you more time and more deals to win one.
Like you, this was my goal when I first started out. I looked at somewhere between 150 and 200 deals before getting my first deal and that was at a time when market conditions weren't as tough as they are now. Ultimately, I wound up doing a 92-unit deal my first time around and realized that part of the reason I was struggling to win deals was simply because I lacked the credibility to be do so. I then decided to modify my criteria to look for deals that were 50+ units and found that I had much more success in that space because most credible bigger buyers aren't looking at deals that are smaller than 100 units. While I didn't want to stay there permanently, it was a stepping stone to build my track record. You may want to consider a similar approach.
While having an experienced PM and knowledge is beneficial for you, it means very little to a broker or seller. Your ability to close means almost everything and you'll need to make them feel confident in your ability to do so if you target bigger deals right out of the gate.
2. Certainty of a buyer's ability to close is always important, but it's even more important right now due to the market conditions. A higher offer from a buyer without a track record is often considered a worthless offer by many brokers and sellers. The only way they would seriously consider a higher offer from an unqualified buyer is if they have no offers from better qualified buyers and their back is against a wall. Submitting real offers that you feel confident actually closing on and having a strong sponsor to work with that has a track record will go much further towards you winning deals.
In short, you can pursue larger deals right out of the gate if you want to, but generally expect that it'll take you longer to win one and make sure you have the right players on your team so that you're prepared to win them and to close them once you do.