more advice on new board

[prepare]

hi guys.

how does the width and thickness of a board affect how it rides? i spent hours this morning looking at 2nd hand boards and came to the conclusion that 80% of the time i have no clue what the board i was looking at was going to be like in the water and weather im going to like it.

my current board is 6'8/19/2.5 and i feel is just to long and heavy for small surf.

i was originally going to go for a 6'1 or 6'2, but today i went out on a really really light and thin 6'7 and found it was terrible paddling into anything over 5 foot.

so basically can anyone educate me on how the thickness and width of a board affects how it rides? Im just dreading spending $400 and then hateing the board in the water.

p.s anyone know any shops around wollongong that let u try before you buy?