I think you need to slow down a little bit. There's lots of different ways to get to where you want. You need to understand how they work and what's involved before deciding what to do. From some of the questions you're asking, it seems that you're missing some knowledge. Do you have any soldering experience? Do you know how a BMS works? Do you know about charging procedures for lithium batteries.
The LCD is plug-and-play. I'm 90% certain it will release you speed limit, but it won't give you more power. The 48v controller doesn't cost much, so it makes sense to get it at the same time to save postage. You'll be able to learn about changing to 48v later, and see which is the best way to get it. The options are: Change to a complete 48v battery, the same type as you already have; chuck the battery (at least the cell-pack) and replace with 12S lipos; modify your battery to increase it to 48v by adding in extra cells and changing the BMS; use a separate booster pack in series with your 36v battery.
The 48v controller should be a direct swap, but it won't work with your 36v battery.
The LCD is plug-and-play. I'm 90% certain it will release you speed limit, but it won't give you more power. The 48v controller doesn't cost much, so it makes sense to get it at the same time to save postage. You'll be able to learn about changing to 48v later, and see which is the best way to get it. The options are: Change to a complete 48v battery, the same type as you already have; chuck the battery (at least the cell-pack) and replace with 12S lipos; modify your battery to increase it to 48v by adding in extra cells and changing the BMS; use a separate booster pack in series with your 36v battery.
The 48v controller should be a direct swap, but it won't work with your 36v battery.