Most of my Intarsias are made using various ?? thick soft and hard woods. When using soft woods I normally use #5 or #7 blades and for hard woods my blades of choice are # 7 or #9. I?ll only use a smaller size blade if I?m cutting a very small piece or when using thinner woods.
I use both Flying Dutchman and Olson PGT blades and like them both.
For someone starting out I would buy the Flying Dutchman-Scroll Reverse type blades. Their Ultra Reverse blades are excellent, however, you have use more pressure to hold down the work pieces because every third tooth, being reverse, will tend to pick the wood up, especially when cutting hard woods.
When buying Olson blades I only purchase their PGT blades which are Precision Ground. They are sharper and will last longer.
You mentioned in your post you thought smaller is better. I find I have better control with larger blades, smaller blades tend to wander more as I use them.
My suggestion is to try different sizes and types and use whatever works best for you.