Best ways to get around Taiwan between cities

Taiwan is a fairly compact country with well-developed transportation system. Most of the population is concentrated in the cities on the west coast. East coast is mountainous and therefore has only a small number of medium-sized cities. These are the best ways to get around Taiwan:

• High speed train
• This is the best option to travel on the WEST COAST (only available on the west coast, actually), including Taipei, Taoyuan, Hsingchu, Taichung, Changhua, Yunlin, Chiayi, Tainan, and Kaohsiung. Should be your first option to consider
• Very comfortable and fast way to travel, and the trip between Taipei to the southern most city Kaohsiung takes under 2 hours
• Much cheaper than flying. The fare from Taipei to Kaohsiung is only around $50 USD, and if you buy in advance you can get up to 35% discount
• To book tickets you need your passport
• High speed trains are all operated by THSRC. Its website is https://www.thsrc.com.tw. You can look up fare, route and schedule info on it and book tickets on it up to 30 days in advance
• Regular train
• Regular train is the best option for traveling in the NORTH and EAST COAST of Taiwan, where high speed train does not serve, including Keelung, Pingxi, Shifen, Yilan, Hualien, and Taitung
• These trains are much slower than high speed trains. From Taipei to Taitung takes 3.5 hours
• But it's very cheap, costing around 1/2 the price of high speed trains
• Trains are operated by Taiwan Railway Administration (TRA). It only operates regular trains and does not run the high speed train system
• Tickets are available for sales 14 days in advance. Some routes frequently sell out (like Taipei to Hualien), so make sure to book as much in advance as possible
• Website is https://www.railway.gov.tw, where you can look up schedule and book tickets
• Driving
• Driving is the best option to explore the mountainous INTERIORS of Taiwan where no trains run, including Taroko National Park, Yushan National Park, Alishan, Sun Moon Lake, Shei Pa National Park. This is especially so if you wish to visit multiple places in the interior
• I personally also recommend driving for the east coast as well. While the roads are very narrow in the north east, the drive is very scenic as you drive right next to the Pacific Ocean through beautiful mountains, cliffs, and many sleepy fishing villages
• Don't drive on the west coast. The scenery is dull because it's all big cities, suburbs, and industrial areas
• Car rental in Taiwan is very easy but it's not cheap. Most rental agencies charge $65-$85 per day (though you can negotiate for discounts). Road condition is excellent and you only need your driver's license and an International Driving Permit
• There are probably over 100 rental agencies of various sizes in Taiwan, mostly local companies. I have a 2019 list of the bigger ones here (scroll to the bottom)
• Buses
• Buses are best used to get to various points of interest around a major city, though intercity bus travels are also available.
• The primary advantage of buses is the low fares, or a good backup option if train tickets are sold out
• For intercity bus travel, use https://www.taiwanbus.tw to find route information
• For tourist shuttle bus that gets you to various points of interest around major cities, use https://www.taiwantrip.com.tw
• Flying
• The only times when it makes sense to fly in Taiwan is when you want to travel between east coast and west coast. For example from Hualien to Kaohsiung. Even then, some routes can be better served by bus
• Domestic flights usually cost at least $100USD for a one-way flight, but some routes cost less than that. The cheapest I've seen is $70USD for Hualien to Kaohsiung.
• I usually use Skyscanner to find the cheapest flights