Great little reel, Matt. I have four. One 103, two 103F, and one R. Love "em all. If you ever decide you don't like it, let me know. I'll take it off your hands sight unseen.
You, being used to centrifugal braking will have a learning curve with Magforce. I think you will find that you will need just a bit more spool tension compared to your Shimano reels. I prefer Magforce braking, and now have only Daiwa baitcasters, for that reason. Once you get used to it, if you do, you will see what I mean.
As far as upgrading and tuning goes, here would be my recommendations, based on my experiences with Daiwa reels.
First thing is a drag upgrade. Carbontex washers are nice, but polishing the metal drag washers is just as good. Doing both is an outstanding thing to do.
ABEC 7 bearings will not make the reel any better at throwing lighter weight baits. The only way to do that is to upgrade the spool, which is an expensive proposition, with limited benefit. I did it once and will not do so again. Nowhere near enough bang for the buck there.
Better bearings will make the reel cast a little better. Basically you'll get similar distances with reduced effort. Reducing casting effort will increase accuracy, so it's worth doing. But, this is already a very capable little machine, and a bearing upgrade is a small improvement. My suggestion; stainless steel ABEC 7's from biggreenfish. I do not like ceramic hybrid bearings. They are not much better than SS 7's and are way too noisy. I think my reels should be seen and not heard.
You have a bearing in each knob. Adding one more to each knob is a small increase in smoothness, and may prove to be beneficial in the long term. My two 103F's have different handles. They came that way. I bought both used. One handle had a bearing at the base of the knob, and a bushing at the top. I replaced the bushing with a bearing to give me a four bearing handle. Nice. The other had a bearing at the top of the knob, and a collar at the bottom, which was non-removable. That one is still a two bearing handle. I don't know which reel had the correct handle, or if these were reels from different years, and thus had different handles. Don't know and have not looked for an answer to the question. I put the two BB handle on my least used Fuego, and put the TD-Z handle from the Fuego on the Alphas.
PXR 6.8:1 gears are now available. Three of my Alphas have these gears. I decided to leave one at 5.8:1 for crankbait duty. After trying the new gears in the back yard, I have reconsidered and will be ordering another set of PX gears for the fourth reel. They are that much better. Faster, which was what I wanted, and smoother which I did not expect.
Adding a bearing to levelwind is virtually worthless. Some report this upgrade makes the reel smoother, and makes the line lay on the spool better. Well, it only costs eight bucks for the bearing and nylon collar, so go ahead if it makes you feel better. It's not going to make your reel perform any better. I even managed to get a bearing on the other end of the levelwind on one reel. I had to do some machining, and make some parts to do that little project, and it was truly not worth the effort. So, I have one reel with a bearing on the gear side of the levelwind, and another reel with bearings on both ends of the levelwind. Both are Fuegos. I have four other Fuegos, and the only time I can tell the difference is when I tear them down for cleaning. There is no functional advantage I can detect.
If you have a Dremel, an assortment of felt wheels and some ultra-fine polishing compound, there are several parts which benefit from a good polishing. Metal drag washers, spool ends, metal clutch components and the tip of the levelwind pawl are all candidates. I have polished gear teeth, but have found this to be an uneven upgrade. One reel turned out much smoother, one was a little rougher, and one showed no difference. I will no longer be polishing gear teeth.
Happy tuning.