As I said before, there is a difference between true character and characterization. True character answers the WHY about characterization. It gives dimension.
It is very possible to create a character --say Jim and give him lots of traits -- he has jet black hair, blue eyes, tall, broad shouldered, drives a Porsche, wears expensive suits, takes his holidays in mountian resorts, and went to a private school. He has two sisters and runs his own company. But in fact this tells you very little about Jim as a person. The why behind the man. In fact, he is very likely to seem wooden.
True character is only revealed when a character faces hard choices. When the author understand the reasoning behind those choices. This then allows the author to make sure the character acts true to type in new and unfamiliar situations. How will the character react to pressure for example. Why will this character fall for the heroine? Where will the conflicts be in their world view? How will they need to change?
For example did Jim acquire these material goods on his own or because his family has always had them? Why did he buy the Porsche? For the speed? For its reliablity? Why does he choose the mountains for a holiday? Does he like the adventure or is it a place that he and his family have gone since time immemorial? If he is a CEO, is it a company that he has fashioned himself or is it one that belonged to his family? One that he has rescued from the brink?
When Jim dates, how does he date? Does he go for fun? For culture? Not date at all? What are his favourite leisure activities?
There is no right or wrong way to do this as the author needs both the characterizartions AND the insight to true character. It is sort of a what came first the chicken or the egg?
One way to help in determining true character is to pay attention to personality theory. for example, you can use either Myer-Briggs or enneagrams. But it is more an either or situation rather than being able to combine the two. The underlying philosophies are very different. Blank slate v inborn traits. Growth arcs v. skill sets
The two books are Please Understand Me ll by David Keirsey for Myer-Briggs and The Wisdom of the Enneagram by Riso and Hudson. Both have valid points. It very much depends on how your mind works. And both can provide the answers to why and how would a person with an underlying character trait react in a certain situation, thus making your character seem more believable.
Myer-Briggs is very much of the opinion that opposites attract. People need other types of people to be whole, and conflicts will arise. It is interesting that it is based on Artistole's four humours and that authors have used this type of personality typing for generations. Keirsey calls them -- Artisans, Guardians, Idealists and Rationalists. The artisans and guardians are much prevalent in society unless you live in the Silicon Valley in which case rationals tend to abound.
If Jim is an Artisan, he will have bought his Porsche for an entirely different reason than if he is Guardian or say rationalist. As Jim owns a company, it is unlikely that Jim will be an idealist and still be an Alpha male. Idealist leadership style is much more subtle. Idealist leaders tend to be catalysts for change, rather than effecting change themselves. They also tend to be brilliant individualists such a writer or a consultant, a mentor type. Thus because Jim owns a successful company, he is probably on balance not an idealist type ( or otherwise there has to be a pretty good explaination WHY he has this company. And if he is an idealist, it will be people oriented. Idealist are a v small percentage of population btw.
So if we stick with the three types:
Jim either bought it for the adventure, the speed, (artisan type) or for
the status, and the security that a Porsche brings (guardian type) or
because he is fascinated by the way it performs, its system., its engineering (rational type). Same car, different reasons. And I would argue it is the reasons that are important rather than the actual car. The WHY.
Next think why does Jim go to the mountains
1. for the adventure (artisan)
2. because he has a large ranch there and it has been in his family for generations (guardian), a place where all his whims can be catered for?
or 3. because, he is interested in nature, the flora and fauna of the area (rationalist)
Next think about the company
1. is it one he founded himself, maybe a leading edge company? (artisan)
2. one he rescued and brought back from the brink of ruin?(guardian)
3. an engineering company that invented something the world can not do without? (rationalist)
1. a bad boy? fun loving or a craftsman? A preformer?
2. a rock steady type? banker?
3. an enginner/geek?
As I go through this process, I can see if the reason are starting to point me towards a specific type or if Jim is all over the place. An all over the place character is less likely to act convincing in a novel than one which derives most of his characteristics from one of the four main groups. Then I can start to know how he will react in other situations, what his strength and weaknesses will be.
I would go so far as to say that the writer who neglects peronality traits (however they develop them) runs the very great risk of creating wooden or incomprehensible characters. But that is just my own opinion.