If you are writing a thesis, look at the style your university is demanding (or else you will be shooting your own feet)
Nevertheless, these are my opinions:
You are doing it right by putting captions -- above for tables and below for figures. And use of
booktabs and ditching vertical lines adds to the taste.
Showing both tables and graphs for the same data may be subjective. If you want to display the exact values and also the trend of variation, both will help. If you have too much data, then showing them through a graph will be a better idea (Reviewers don't read/like too much data). Further, space constraints influence this issue to some extent. Personally I am against showing both.
Thesis (report or book)
In a big document like thesis, it will be better to put the figures and tables close to where they are mentioned in text. By using the options
[htb] you are giving latex more freedom to adjust float placement (at which latex is good). Stacking several floats in the same page is only a matter of personal preference and as long as it doesn't destroy readability, I don't find any thing wrong in it.
Also, it will be better to have a LoT and LoF if you have a large number of those things. It will make navigation much easier. They are generally put in the front matter (place where your certificates, preface/abstracts come), after the table of contents.
If you are submitting your article to a journal/conference, beware of the style they want. If it is the case, you don't have freedom but to use their style file.
As space may become a constraint here, putting both graph and table should be avoided.
Whatever is written above for figures is still valid for floats, here also. Now the inclusion of LoT and LOF will become a matter of personal preference. As your manuscript may not grow beyond, say, 20-25 pages, I feel that they won't be necessary.
[p]where needed (wrong placement, extra white space, etc.).