some people make their landing pages look like the vendor site and some dont. You will have to test various styles for each product to see what works best
For example:
I promote a product on CB that is in the garden niche. I made my landing page and seen about 2 sales a day.
I then changed the background color of my LP to the exact same color as the vendors site. I then seen a spike in sales to about 4-6 a day on average.
I then added my opt in box this week and seen 0 sales. I am now tweaking the content and location of the opt in box....if I still see 0 sales then i will get rid of it.
Some niches/products simply do not work well with opt in for some reason but you still need to test
to be honest, I would rather make only 1 sale a day and build my list by 100 per day than make 10 sales a day and not get a single email....