I want to buy some shoutouts for my mountain bike account, but how should I design the shoutouts? Should I go for a video, or a gallery, or do I want the shoutout to blend in and look like a regular post? And what about the caption?
As you see, I have a lot of questions and I’m open to having a discussion about the best shoutout design.
I will follow this topic, Good question, I hope someone expert will answer you.
For shoutouts
It is generally better when you have the same content posted in your profile already.
This will create reliability to the people who come to your account from the shoutout pages.
Regarding the design:
I did a quick search and found this; which can be a great example.
To get the maximum out of the shoutout, comparison between A and B or carousal can help get you more attention.
Example: https://www.instagram.com/p/B2j_R0gne0W/
https://www.instagram.com/p/B2zdCZwni3U/
compared to their other content engagement:
https://www.instagram.com/p/B27NHhIBgMf/
If you choose to go for video, then
do choose the ones which shows catchy content (like bike tricks).
Regarding blending in to the page’s theme, it is advised to but not necessarily. Content that doesn’t match to the page’s design is a gamble. It can go very bad or very good.
following to lurk 
Look at what other successful influencers do and copy them. Then add your own twist.