Parametric Design enables designers to formulate and explore new ideas through parameters, typically by manipulating numerical values. However, visualising and exploring the design space of an established parametric design solution is natively difficult through desktop displays for designers due to screen space constraints and requiring familiarity with visual-language programming interfaces. Thus, we sought to explore Virtual Reality (VR), inspired by Natural User Interfaces (NUI), to develop and explore new interfaces departing from traditional programming interfaces, that could complement the spatial and embodied affordances of contemporary VR devices. Informed by two industry-led focus groups with architects we developed and examined the usability of three different interfaces: 1) \textit{Paramaxes}, an axes-based interface that allows designers to distribute and manipulate parameter visualisations around them in physical space; 2) \textit{ParamUtter}, a Voice-based User Interface (VUI) that allows designers to manipulate parameter visualisations through natural languages; 3) \textit{Control Panel}, which presents the parameters as sliders in a scrollable pane and acts as baseline comparison. We ran an exploratory study with experts and found that the \textit{Control Panel} was ultimately the preferred interface for a design manipulation task. However, participants commented favorably towards qualities in the unconventional interfaces, with \textit{ParamUtter} scoring highest in System Usability Scores (SUS), and participants valuing the potential of using physical space to explore design spaces with \textit{Paramaxes}.