Quick question: If I add an extra 30 lbs worth of weight, will it make a big difference in how my bike performs? I'm starting from 200 lbs and going up to 230ish

In very simplistic terms, force equals mass times acceleration (F=ma). You're talking about increasing m by 15% so you either need 15% more F to get the same a, or the same F will give you less a. Climbing hills will give you a similar issue where the energy you need to lift the weight will also increase, but on downhills you should notice yourself accelerating faster.

The bike will perform the same. You on the other hand may not. Why would you be interested in packing on weight when everyone else is looking to take it off?

It's not my weight, I'm thinking of motorizing my bike to use on half of my commute. I'm looking into possible negatives regarding handling and performance with regular pedaling

Aside from the extra effort required to push everything around, the centre of gravity will change as will the steering stability. How much that gets affected really depends on the geometry of the frame and how you distribute the weight. You might want to visit the touring forum. 230 lbs is OK as long as the wheel build is suitable and you keep your speed down over rough roads. Touring bikes tend to have heavier, stronger frames than straight recreational bikes in anticipation of an extra load. Suggest you also check the load rating on your tires and adjust the tire pressure accordingly.

Assuming no change in your front profile, your top speed will stay similar. You might lose a SLIGHT amount of top speed. Your acceleration, however, will suffer, and you will work harder to get up to speed.
Clydes ride with well over 230 on their wheels all the time. As long as you don't have a low spoke count wheel you should be fine.

Just buy a motorcycle. Then you can put on 30 lb. and fit right in to a whole new crowd.

Waddle, waddle, waddle...

Loud pipes are annoying.

You might post your question on the electric bikes forums.

Pig in a Poke there , what bike ? what motor kit ?

how about buying something already motorized, ?

They have several on the LBS floor, already sorted out.
Then you just have to Pay for it.

Depending on the bike you may not even need to keep your speed down over rough roads. When I started riding the weight of me plus the bike was somewhere north of 300 pounds and it wasn't long before I was going over rutted gravel at reasonable speeds.

I have ridden with lots and lots of weight strapped in various places on many different bicycles. When riding on flat ground I have often forgotten the weight was there. As soon as the road tilts the least bit upward, however, I remembered.

As mentioned above, discuss your plan in the Electric bicycles forum.

I frequently commute and run errands with loads approaching 30 lbs. Not a big deal, but it does take more work climbing hills.

I'm not sure of details yet. To be honest I'm actually leaning against the whole idea because of theft concerns

It'll affect your acceleration and hill climbing ability, and I'd think little else. The good guys on the electric bike forum would likely be able to provide more info

There are quiet motorcycles.

https://noping.net/english/

30lb will reduce maneuverability for things that require you to move the bike under you.