One edit, three Google Ads sizes: 16:9, 9:16 and 1:1 on Timeline

Google Ads' video specs page lists 16:9 at 1920 by 1080, 9:16 at 1080 by 1920 and 1:1 at 1080 by 1080, with 15 seconds recommended for in-stream and in-feed video. Timeline 1.0 can render one edit at each size by changing the output width and height, at $0.10 per output minute rounded up.

The three shapes

A 15 second render is billed as one minute, so three renders cost $0.30 at the docs' rate, whatever the shape.

Choosing fit

Timeline video[].fit is cover (default), contain, stretch or blur. cover fills the frame and crops what does not fit. blur keeps the whole picture and fills the rest with a blurred copy. contain adds bars, and stretch distorts, so skip both for ads.

Output width and height accept 256 to 2160, and fps 24, 25, 30 or 60, so the three Google sizes are in range. Transitions available are fade, wipeleft, wiperight, slideup, slidedown and dissolve, at most one second.

Limits

Cropping a 16:9 shot into 9:16 keeps about a third of the width, so text near the edges is cut. Look at each render. Captions are better burned in after the crop than before, which is why the Video captions API takes a finished clip.

Sume does not choose the crop for you, and the docs list no subject tracking. The three renders are three separate jobs.