It is interesting to see that in the pagebuilder arena we don’t seem to care much about the sizes of the themes/plugins we install. It is hard to make a clear statement on their performance influences.
But let us at least figure out what your choices are on installing stuff above the base of WordPress. About 9 years ago WordPress 2.1 was about 3MB. WordPress 4.5.x is about 23MB.
After a long roadmap in digging through numorous themes I ended up with Genesis, which is just about 1MB. After using pre made ChildThemes I started using Dynamik Website Builder from CobaltApps. Dynamik counts for 2,9MB. That all seems reasonable, compared to the base installation of WordPress, but without knowing the effect on performance.
For sure the combination Genesis/Dynamik can be called light-weight, compared to all fancy full-featured ready to go themes like Bridge, which are offered together with a couple of heavy-weight plugins like Visual Composer and LayerSlider (those two alone already add up for 14,8 + 8 = 22,8MB, about the size of a clean WordPress install).
MB’s and speed
Beaver Builder plugin needs 14MB and the Beaver Builder theme needs 5MB space. Together that is 19MB. We used Genesis/Dynamik a lot in combination with LayerSlider, which consumes 1 + 2,9 + 8 = 11,9MB. Stepping over to the BB Pro package consumes 19 MB. Yes, that is much more, but you must have a look what other plugins can be avoided, looking at the various modules BB plugin has to offer. Also keep in mind that LayerSlider is a much more advanced slider plugin compared to the slider content module in Beaver Builder.
GeneratePress is a relative new theme mentioned a lot in the various Facebook groups around pagebuilders. It integrates very well with Beaver Builder plugin and comes with a basic ChildTheme. GeneratePress is like Genesis also light-weight with 1,5MB space. The GP Premium plugin (2MB) adds about 12 premium functions to the theme. Together with BB plugin this solution takes 22,5MB.
Above the Beaver Builder plugin the following add-ons became available in the last 2 months and can be added up to the above solutions: