In the Wordtracker Find Keywords tool, under Options, which Match Type should you use - "Keywords in any order" or "Exact keyword inside a search term"? Also, should "Include plurals" be checked? By default they seem to leave it off. Which will give you a better list of keywords, with plurals or without?
They also have an eBook about keyword research. It's called "Masterclass". There, they recommend using "in any order".
Not to sure about Wordtracker as I haven't used them in years ever since they did away with the shorter subscriptions, but IMO you should use both. Their strong point is list building. You should always try to build the biggest list possible first and filter your targeted keywords from there. Their KEI way of filtering gives a more overall strength of competition (IMO unless it's changed). In other words it'll give you a "guesstimate" of the competition of 10,000 + sites, but unless there's a REALLY huge number of searches you're only competing with the first page of the SERPs. That is unless you're driving traffic by other means as well.
Don't get too precious about specifics of keywords. Most keyword research is based around samples. Only by operating and competing in a keyword market will you get a genuine feel for what is really going on.