Around 2016-2017 I prototyped an app for Android & IOS that pulled patient data from an oracle database and supplied that data to a GUI. At first I planned on using FMX exclusively for screens, but found that although the screens worked well, they were most definitely not performant with FMX controls and screen draws. So I went back to the drawing board and utilizing Oracle stored procedures, kbmMW (middleware, awesome!), and the web browser control on both platforms, I pulled the data in the stored procs, built HTML in the stored procs, used kbmMW to ship it to the clients, and created a tabbed interface using native controls, with all content areas displayed in the embedded web browser.
The generation of the html in Oracle was instantaneous, the transfer of the html content using kbmMW was instantaneous on the local network, and display performance was quite good. I've heard that SKIA has better performance for UI draws; since we are talking about small device graphics, UI performance will always be an area that requires special attention. As the examples above show, Delphi is quite capable of creating complex, highly performant mobile UI's; minimal conditional defines are required, all of your existing Delphi source/servers/application logic is available to you. It allows you to work within a familiar environment, utilizing ONE(1) toolchain - albeit with some 3rd party stuff potentially - and has excellent performance.
The cost of using Delphi for mobile is really measured not in the purchase price of Delphi, nor of 3rd party components, but in the learning curve. It's a different programming paradigm, so the ability to utilize just ONE(1) tool that you are familiar with greatly minimizes the time to learn how to work with mobile. Native combined with RAD will get you to the expert level with mobile faster than other environments/languages/tools with which you may not have any experience.
Another nice example app: https://www.linkedin.com/posts/piotr-stefanowicz-035465294_delphi-tms-web-core-pwa-prodvisor-application-ugcPost-7283126982035345409-m4HG?utm_source=share&utm_medium=member_desktop